654 



ANIMAL HEAT. 



ture of the different classes, the results of which 

 have been already stated. The comparison 

 might he carried out in regard to Insects and 

 the Mollusca, which present some appreciable 

 differences. If attention were confined solely 

 to the structure of the greater number of the 

 organs of nutrition, which are much more 

 laruely developed in Molluscs, it might be 

 inferred that they had a higher calorific power 

 than Insects; but when we take into the account, 

 1st, the final result of the nutritive functions, 

 the quality of the tissues, which in the Mollusc 

 are much more loaded with watery fluid, by 

 which they acquire a greater degree of softness 

 and flaccidity, (whence the class has its name,) 

 whilst in the Insect they are, on the contrary, 

 as remarkably dry and firm ; 2d, when the 

 most general mode of respiration is compared 

 in the two divisions, it being in the Insect 

 aerial, in the Mollusc aquatic ; 3d and lastly, 

 when we glance on the one hand and on the 

 other at the state of the nervous system, and 

 observe how much less perfectly this is developed 

 in most of the Molluscs than in the Insect, it is 

 impossible not to perceive that according to the 

 principles influencing the production of heat, 

 the Mollusca must be inferior in this respect 

 to Insects. This is indeed the result of obser- 

 vations of all kinds, however imperfect or 

 limited these may have been, as we have seen 

 above. 



It is impossible to carry the comparison 

 further; the phenomena connected with heat 

 in the lower grades of the animal creation 

 become inappreciable; and this even in virtue 

 of the same principle that has been an- 

 nounced ; for the tissues are found to become 

 more and more watery as we descend in the 

 scale, till at length the solid constituent is 

 almost inappreciable. Of course the circulating 

 fluid must be watery in a still greater ratio; it 

 contains but few globules; and then the ner- 

 vous system falls off in a still greater propor- 

 tion ; it becomes more and more imperfect, till 

 at length no trace of it is to be discovered. 

 We thus arrive at the last links of the chain, 

 after having run over the whole animal king- 

 dom, and we have found one uniform principle 

 of correspondence between organic modification 

 and calorific power. It were difficult to imagine 

 any more satisfactory proof of a principle than 

 has been afforded ; indeed as this has on no 

 one occasion been found belied, we are fully 

 authorized to regard it as established. 



We hare as yet examined but two points in 

 reference to animal heat; 1st, the temperature 

 of man and of the different classes of animals; 

 2d, the general relations of organization with 

 the production of heat. In mentioning the 

 temperature in any case, we have spoken 

 of it as determinate ; and farther, to have data 

 that should be always comparable, the tempe- 

 ratures have been taken regularly in the same 

 places, viz. the mouth in man, and the other 

 extremity of the intestinal canal in animals. 

 We have still to ascertain whether the tempera- 

 ture varies or is identical in different parts of 

 the body. 



Temperature of different parts of the body. 



There is no need of the thermometer to tell 

 us that all parts of the body do not at all times 

 preserve the same temperature. We are 

 often certain that the extremities are colder 

 than the trunk for example ; and a law of 

 decrease of temperature in the ratio of the dis- 

 tance of parts from the heart had even been 

 deduced from this observation. But when 

 exact measurements came to be taken, this law 

 was soon found to be at fault, as will be seen 

 by-and-by in the course of these observations. 

 Dr. Davy, in taking the temperature of the 

 different parts of the body of a lamb, found 

 that of the right ventricle of the heart 40, 5 

 (105 F.), that of the left ventricle 41, 1 (106 

 F.). The left ventricle was therefore higher in 

 temperature than the right to the extent of a 

 degree of the scale of Fahrenheit's thermometer. 

 The temperature of the rectum corresponded 

 with that of the right ventricle. 



In my inquiries along with M. Gentil 

 into the relations in point of temperature of 

 certain external parts, we found in a strong 

 man, perfectly at rest in mind and body, 

 in the month of July, the external air being at 

 21, 25 c. (71 F.), the temperature of the 

 mouth 38, 75 (102 F.) ; that of the rectum 

 corresponded. The hands presented the next 

 highest degree, marking nearly 37, 5 (99, 5 F.). 

 What is remarkable is that the axilla; and 

 groins, which corresponded with one another, 

 were very sensibly lower in temperature than 

 the hands ; they did not raise the thermometer 

 higher than 36, 90 c. (99 F.). The cheeks 

 marked 35, 93 (96, 5 F.), the temperature 

 being ascertained by enveloping the bulb 

 of the thermometer in the skin of these 

 parts. The feet were a little lower, 35 62 

 (about 96 F.) ; their temperature being deter- 

 mined by placing the thermometer between the 

 two, so that the bulb was surrounded on every 

 side. The temperature of the feet was, there- 

 fore, notably lower than that of the hands, 

 differing to the extent of 1, 88 of the centigrade 

 scale (above 3 of Fahrenheit's thermometer). 

 Placed on the skin between the thorax and 

 abdomen the thermometer was at its minimum, 

 not rising higher there than 35 (95 F.) ; but 

 here a part of the bulb being in contact with 

 the air, there must have been considerable 

 cooling. 



As the question here is not of absolute but 

 merely of relative temperatures, we can make 

 great use of the results come to by the different 

 writers quoted. We shall present a summary 

 of these under the following head. 



Relations between the temperature of inter- 

 nal juirts. 1st. The warmest part of the body, 

 according to John Hunter, is in the abdomen 

 close to the diaphragm. 2d. The next part in 

 point of temperature is the left ventricle of the 

 heart. 3d. The right ventricle of the heart is 

 the next in succession. The rectum and the 

 mouth shut are of the same temperature. The 

 greatest difference consequently between the 

 temperature of these internal parts does not 

 amount to more than 1 centigrade, or at the 

 utmost 2 Fahrenheit. 



Supposing the relations in temperature of the 



