CHAP. V. from it, as an ossification of the valves, polypous concretions, or enlarging SECT. III. or thickening of the substance of the heart, or an accumulation of matter CIRCULA in the pericardium, or an aneurism. In the latter cases the predisposition to faint must be cautiously anticipated and guarded against, as well by medicine and sedatives as by other regimen. (n) TION. Of hereditary dis eases through the medi um of the blood.(0) Of infu Some authors attribute the unhappy prevalence of hereditary diseases. or predispositions towards diseases, and even insanity, to the influence of the blood; and Dr. Good observes, that if the blood be once impregnated with a peculiar taint, it is wonderful to remark the tenacity with which it retains it, though often in a state of dormancy or inactivity for years, or even entire generations, for as every germ and fibre of every other part is formed and regenerated or renovated from the blood, there is no other part of the system that we can look to as the seat of such taints, or the predisposing cause of disorder.(p) We shall hereafter have to enumerate the disorders which are considered hereditary, and to suggest the counteracting remedies. We must, however, here notice that there are many hereditary diseases which it is insisted are not attributable to any taint in the blood, but rather to some affection of the blood vessels themselves, or the absorbents, or the nerves, and not to the blood itself. (p) It has been ascertained that medicated liquids, injected into the blood, sion, trans- exert their specific powers exactly as when swallowed, and purgatives and fusion, or emetics, so administered, empty the stomach in like manner as if swalinjecting of lowed. (q) The artificial infusion or transfusion of a minute portion of any liquids into even mild fluid into the blood, may occasion the most dreadful symptoms, the blood. such as palpitation, convulsion, &c.(r) Hunter appears to have considered that the blood of man and all warm-blooded animals is nearly alike;(s) and hence it would seem that the blood of a healthy animal might in case of exhaustion from hemorrhage, be usefully applied; (t) at least it appears to be established, that the infusion of healthy human blood of another person is not prejudicial; but in case of exhaustion and loss of blood from hemorrhage, the infusion of it into the vein through the double pump, otherwise employed for emptying the stomach, or a common syringe capable of holding four or six ounces, will frequently save life.(u) Of animal ture. We have partially considered the subject of temperament and temtempera- perature.(2) Although the definitions in the books of those terms are nearly similar, yet strictly the subjects are dissimilar; for the varieties of temperament depend as much on the mental as the corporeal structure, though not, as the ancients supposed, merely on the state or quality of the blood,(x) whilst animal temperature, in the sense here used, is peculiarly a state of the blood, and in comparison with the surrounding atmosphere, it is the power and degree which the living animal, and in particular mankind, possesses, of resisting, to a certain extent, the changes of the external temperature, or of maintaining a more or less uniform (n) 4 Good, 377. (0) See Part II. of Hereditary Diseases. (g) El. Blum. 21; 2 Good, 40; 1 Bost. (r) El. Blum. 366, note (e,) an account of the direct infusion of a material unassimilated, instead of the regular more gradual introduction, through the absorbent vessels; and see 2 Good, 40; as to the (u) El. Blum. 21, 22; 2 Good, 57; 3 Bell, 250, 251; and Hunter on the Blood, 13; 4 Amer. Jour. Med. Sci. 224, 226. (x) As to temperament, ante, 49; and as to temperature, ante, 112, 113. degree of heat, independent of that of the air, and of the substance with which it is in contact. It is an unquestionable fact, that whilst the body is surrounded by an atmosphere which is frequently 40, 50, or even a greater number of degrees colder than itself, so that the heat must be constantly rapidly abstracted from it, yet that it possesses the power of continually supplying the loss thus occasioned, and of continuing that degree of internal animal heat which is so essential to life, thus constituting one of the principal distinctions between animate and inanimate bodies. We will first state the usual degrees or state of the temperature in man, and then shortly examine the causes of this singular difference between external and internal temperature. CHAP. V. SECT. III. CIRCULA- heat in All animals and mankind have a power of generating heat as well as The usual cold, so as efficiently to adapt the frame to the external medium under temperaall ordinary circumstances. The natural and ordinary temperature of ture or debirds is the highest, and about 107 or 108 degrees; that of the viviparous grees of quadrupeds is about 100 or 101 degrees, while the human temperature mankind. is a little lower, being 97 or 98, or according to Blumenbach, 96 degrees;(y) whilst Dumas insists that it ranges from 87 to 108 degrees, though he fixes the habitual degree at 95 or 96;(z) and Magendie supposes that the variations to which the human temperature is subject, depend upon constitution, temperament, &c. He also agrees with Dr. Edwards, that the arm-pit (being the external part nearest the heart, and the least exposed, and therefore most likely correctly to represent the internal heat in the centre) is the proper situation for applying the thermometer in order to ascertain the temperature of the individual.(a) In the saine climate, however, there is not, in general, according to Magendie and Dr. Edwards, much difference between the temperature of different individuals; but during infancy it is even 3 or 4 degrees less than in the adult.(b) In all it becomes gradually higher towards the spring, and gradually sinks towards and during the winter. (b) In acute fevers may increase several degrees, and it has occasionally risen even to 120 degrees, but such instances, it is said, are rare, and the increase is seldom beyond 107 degrees, (c) and Hunter has remarked, that the actual temperature in inflammation is not so much increased as the sensation would seem to indicate. (d) it The ancients erroneously supposed that the cause of the greater inter- Causes of nal heat, compared with that of the atmosphere, was an innate or pri- the intermary quality of the heart. That doctrine was first denied by Mayow, nal tempe who first attributed its true cause. (e) The experiments of Black and rature differing from Crawford throw further light upon this subject, and the now esta- the exterblished(f) doctrine is, that the source of animal heat is principally in nal the action of the air upon the blood, and that it ultimately depends upon the abstraction of carbon from that fluid, and the conversion of oxygen into carbonic acid:(g) so that it is the union of oxygen and carbon that produces heat. But it is admitted, that with respect to the mode in (y) El. Blum. 96; and therefore warm baths are usually regulated at that degree, termed blood heat. (z) Dumas, Physiol. chap. vi. tom. iii. p. 126. (a) Magendie; Physiol. tom. xi. p. 403. (b) Id. ibid.; and see observations of Despretz, in Edin. Med. Journ. vol. iv. p. 185. (c) Currie's Medical Reports; and Ed. Med. Journ. vol. xxii. p. 363; Dr. Edwards, Phys. tom. ii. 400, 490. (d) Hunter's Animal Econo. note to pages 113, 296, &c.; see fully 2 Bost. (e) Mayow's Tract. p. 151, 256, 257; (f) But see the different opinions entertained at different times, 2 Bost. 192 to 246. Hunter, in his Treatise on Blood, appears to doubt the cause of heat, see p. 15, (g) 2 Bost. 192 to 246; and see Copl Dict. tit. Blood, 189. SECT. III. CHAP. V. which the heat is distributed through the various parts of the body, we are still unable to form a decisive conclusion. (h) It is further considered, that the nervous system affects the temperature, but that it is by an indirect operation, in as far as it contributes to bring the air into contact with the blood. (2) We have seen that the lungs regulate the temperature;(k) they are the apparatus by which the heat of the system is evolved, and its temperature regulated, either by an increase or decrease of heat, and this is accomplished by the discharge of carbon and water, (1) the first depending upon a chemical combination of the oxygen of the atmosphere with a portion of carbonaceous matter, by which combination heat is necessarily extricated; the second, upon the abstraction of a portion of the heat thus extricated, in consequence of the evaporation of water from the surface of the pulmonary cavities;(m) the perspiration of the skin materially assists in this cooling process, as it serves to abstract the excess of caloric.(n) It appears to be established, that when from any cause the conversion of arterial blood into the venous state is impeded, as was observed by Hunter to take place during fainting, the temperature is always lowered, and consequently sometimes shivering, or a state of chill is experienced. (0) (h) 2 Bost. 229 to 246. (i) Id.; Stevens on Blood, 29, 39, 40. (1) Id.; Stevens on Blood, 39, 40. (m) See the observations and authori ties, 2 Bost. 240. (n) Id. 241. (0) Hunter on the Blood, 68; 2 Bost, 220; 4 Good, 373 to 378. CHAPTER VI. OF THE FUNCTION OF DIGESTION AND ITS SEVERAL ORGANS. Section I. Of the Alimentary Canal and Digestion in general. Section II. Of the Organs of Mastication and Deglutition, and their Func tions. Section III. Of the Organs of Digestion and their Function, namely, the Sto- CHAP. VI. SECTION I.-OF THE ALIMENTARY CANAL AND DIGESTION IN GENERAL. SECT. I. OF THE GENERAL. As the suspension, for a time, of the function of digestion, would not Alimentaoccasion instantaneous death, it has usually been regarded as in a degree RY CANAL of less importance than the functions which we have previously consi- AND DIGESdered, but as the human frame cannot long subsist without a supply of TION IN nourishment and new materials, the function of digestion is, in truth, as important for the well being of the human frame as those which are treated as of more primary consequence. It has been correctly observed, that digestion, absorption, and secretion, are so connected, that it is impossible to give an account of one, without presuming upon a certain acquaintance with the other; for the secretion cannot be formed until the blood has been already elaborated by the digestive and assimilating processes; while digestion, in its turn, cannot be effected until the stomach has secreted the gastric juice, the principal secretion and chief agent in converting aliment into the materials of the blood.(a) As, however, there are peculiar organs for digestion, and for absorption, and for secretion, we will examine each subject separately. Digestion, in its most extensive sense, is that function or process by Digestion which aliment is made to undergo a succession of changes, so as to adapt defined it for the purposes of nutrition, though that word (from digestio) in its and its primary import, merely signifies the operation by which the food is con- eight seve ral parts cocted in the stomach. Magendie, in his work, treats digestion as con- described. stituted of eight subordinate actions, namely; 1st, reception of the food; 2d, mastication; Sd, insalivation; 4th, deglutition; 5th, action of the stomach; 6th, the action of the small intestines; 7th, that of the large intestines; 8th and lastly, the expulsion of the fæces; and that of these, the 5th and 6th are to be regarded as the most essential operations.(b) These collectively, but principally the 5th and 6th, acting upon the received food, create chyme, and afterwards chyle, which are the essential ingredients for keeping up the supply of new blood, and which, with perhaps some nourishment introduced externally through the pores of the skin by absorption, recruit and sustain the human frame.(c) The whole Alimentaof the process of digestion is carried on in the alimentary canal, which ex- ry Canal. tends from the lips and mouth through the whole range of the pharynx, cesophagus, (vulgarly gullet,) and into and through the stomach and the whole range of the intestinal canal, including the small and large intestine, (a) 2 Bost. 248. (b) Magendie, Physiol. tom. xi. p. 33; 2 Bost. 342, note. (c) 3 Bell's Anat. 236 to 238. CHAP. VI. and terminating at the extremity of the rectum, the anus. In the mouth, SECT. I. where this alimentary canal commences, it is comparatively wide; it conALIMENTA- tracts in the oesophagus, which is about an inch in diameter, it then widens BY CANAL in the stomach, and then again contracts into the tube of the intestines. (d) As man can sometimes subsist for several days without fresh aliment for digestion, this function is comparatively subordinate to respiration and circulation, but as the frame cannot long be sustained in complete abstinence, digestion is substantially as important as those vital functions. We will first consider every organ and part employed in this function and its peculiar office in regular order, descending from the highest to the lowest. These may properly be divided and considered as those which are above the diaphragm, and those below. Those above, are, from the lips inclusive, through the mouth, fauces, and pharynx, and down the oesophagus or gullet, through the aperture in the diaphragm; and those below, are the stomach and the small and large intestines, and all the contents of the abdomen to the anus for discharging the fæces, together with the different viscera.(e) In the organs above the diaphragm, and especially in the mouth and fauces, are performed the two important offices of mastication and deglutition, which, after examining the organs themselves, will be considered. In those below, the masticated and deglutinized food is digested by being first, through the influence of the gastric juice, converted in the stomach into a uniform pultaceous mass, called chyme; and afterwards, when separated in the duodenum, being the first portion of the small intestines, by the influence of the mixture of bile and pancreatic juice, is converted into chyle and other liquid secretions, and the chyle is taken up by the absorbent vessels, and carried into the thoracic duct, and from thence into the subclavian vein, and then into the right auricle of the heart; whilst the effete and useless parts of the aliment are in the larger intestines converted into fæces or excrement, and finally carried off as waste in the manner presently explained.(ƒ) SECT. H. SECTION II.-OF THE ORGANS OF MASTICATION, DEGLUTITION OR SWALLOWING INTO THE STOMACH, AND THE FUNCTIONS THEMSELVES. Of the Or gans of Mastica tion, De glutition or Swal As there appears to be a natural and obvious division of the alimentary canal between that part above and that below the diaphragm in the different functions performed in each, we will divide the subject accordingly,the upper division containing the organs of mastication and deglutition, and the lower division the proper organs of digestion, namely, the stomach, &c. The organs in the upper division, of mastication and deglutition, inthe Func- volve the consideration of, lowing into the Stomach, and |