PHYSIOLOGY. 



usual, for both the pulse and respiration 

 became slower. Mr, Hunler made many 

 experiments on this subject, and conclud- 

 ed, that there is always an exertion or 

 expense of animal power in resisting cold 

 proportioned to the necessity of the case ; 

 that this exertion is in proportion to the 

 perfection of the animal, and to the de- 

 gree of heat natural to the species and 

 that it is independent of circulation, voli- 

 tion, and sensation. 



The power of resisting heat arises from 

 the evaporation that is constantly going 

 on from the surface of the skin, and 

 which becomes extremely abundant when 

 the temperature of the air is much raised. 

 Seethe account of the organ of touching. 

 This is a very powerful means of dimi- 

 nishing animal temperature, and conse- 

 quently, when long continued, has a very 

 weakening effect. Of fourteen persons 

 shipwrecked in December, three sat on 

 the deck, out of water, but exposed to 

 sleet, snow, and wind; the evaporation 

 from their surface must have been im- 

 mense, and they died. All the others 

 were. up to the middle or shoulders in 

 "the water for twenty-three hours, yet 

 survived. 



Animal heat may be altered from its 

 standard by external applications or dis- 

 ease; but the change can be carried 

 much further below the standard than 

 above it. A man could bear to have his 

 penis cooled to 50 ; but it could not be 

 heated beyond 100 J ; although the heat 

 employed raised a dead penis to 114. 



Secretion. The blood, circulated in the 

 manner we have just mentioned, ami pre- 

 pared by the organs of respiration, is the 

 source from which the various fluids of 

 the animal body are formed in the pro- 

 cess of secretion. 



The various arrangements of these pro- 

 ducts are, in a great measure, arbitrary. 

 Milk seems to be formed by the most 

 easy process, as it resembles so strongly 

 the nature of chyle. Next come the wa- 

 tery fluids ; (so called from their appear- 

 ance, although in composition they differ 

 considerably from water, chiefly in con- 

 taining albumen). The humours of the 

 eye, the tears, sweat, lymph of the cellu- 

 lar substance, vapour of the thorax, ab- 

 domen, and pericardium, and the water 

 of the ventricles, belong to this class. The 

 urine seems to come under the same 

 head, although it is of a peculiar and com- 

 pound nature ; next follow the salivary 

 and pancreatic juices ; and then the mu- 

 cous fluids poured into the alimentary, 

 respiratory, and generative organs. The 



fat, marrow, grease of the skin, ear- Wax, 

 sebaceous matter of the eye-lids, and 0? 

 the external organs of generation in both 

 sexes, constitute the class of adipous flit- 

 ids. The liquor of the amnion, the syno- 

 via of the joints, and the prostatic fluid, 

 are of a gelatinous kind. The male semen, 

 and the bile, are both of a very peculiar 

 nature. The chemical analysis of these 

 fluids will be considered under their pro- 

 per articles. 



These very various products are sepa- 

 rated from the blood by very different 

 organs. The most simple mode of secre- 

 tion is that performed by the arteries of 

 a part without any glandular apparatus ; 

 as the fluids of circumscribed cavities, 

 the lymph of the cellular substance, and 

 the fat and marrow. 



Secretion is more complicated when 

 performed by means of certain organs 

 culled glands. The most simple of these 

 are the mucous follicles, found in various 

 parts of the alimentary and respiratory 

 canals ; consisting of a small bag receiv- 

 ing the secreted 'fluid from the arteries, 

 and expelling it through a short excreto- 

 ry duct. But the name of gland is applied 

 more properly to the larger organs of 

 complicated structure, as the pancreas, 

 breast, salivary glands, &c. These, con- 

 sisting of an aggregation of minute parti- 

 cles, are called conglomerate, to distin- 

 guish them from the lymphatic or con- 

 globate glands. Each of them possesses 

 an excretory duct, made up by the union 

 of branches from the various component 

 portions of the gland. The larger por- 

 tions, into which each gland is resolved, 

 may be divided into smaller and smaller 

 particles, and ultimately into very minute 

 portions; concerning the structure of 

 which, anatomists have warmly disputed. 

 Some describe them as being hollow, and 

 called theni acini, or cryptse; while 

 others asserted that they consist merely 

 of convoluted blood-vessels : the latter 

 opinion is the most prevalent at present. 

 The structure of the liver and kidney is 

 analogous to this, in its minute parts : 

 both these organs, and particularly the 

 latter, exhibit the acinous appearance. 

 The ultimate blood-vessels are arranged 

 in very different ways in various glands ; 

 coiled up in roundish masses, as in the 

 kidney, arranged like stars in the liver, 

 and forming an appearance like a camel's 

 hair pencil in the spleen. 



The various properties of secreted flu- 

 ids depend, no doubt, more on the inte- 

 rior texture and vital powers of the se- 

 creting organs, than on their external ha- 



