290 NATURAL HISTORY OF ORGANIZED BODIES. 



field for stud}', if we acquire new processes with which to explore it. It is 

 cLietly when we recur to ancient experiments that we are struck with the pro- 

 gress which has been realized. We might almost be disposed to condemn the 

 narrowness of view of the old experimenters, if we did not revert in thouglit to 

 the epoch when they lived, and to tlie exiguity of the means of analysis of which 

 they could avail themselves. 



6till another reason necessitates the erajdoyment of apparatus in physiology. 

 Even in the cases in which vivisection reveals to us important facts, it induces 

 such extreme perturbations in the functions of life as greatly to modify them 

 and to convey a false idea, if the normal expression of the function l)e assumed 

 to 1)0 exliibited in any phenomenon which we may thus witness. To take an 

 example, the case may be cited when tlie section of the spinal marrow' is per- 

 formed on an animal, and artificial respiration is practiced in order to maintain 

 organic life as long as possible. Under tliese conditions the phenomena of cir- 

 culation undergxi so profound a modification that we should be on our guard 

 against the false ideas wdfich may be drawn from the experiment. The rapidity 

 of the current of the blood becomes excessive, the pulsations of the heart are 

 accelerated, the central temperature is lowered, while the peripheral temperature 

 rises. The physiologist should, therefore, endeavor to inflict on the animal 

 which he is exannning as little mutilation as possible, if he would obtain an 

 exact idea of the normal conditions of the circulation of the blood and the 

 aiiinuil temperature. "VVe know, moreover, that the secretion of the glands, 

 under normal conditions, difiers much from that which we collect by artificial 

 means. Tlius the pancreatic juice derived i'rom an animal in which an opening 

 has been effected difiers chemically from that wliich the gland discharges nor- 

 mally into the duodenum. It would not be difficult to multiply exam})les shoW' 

 ing how necessary it is to leave the animal in its normal condition if we would 

 not have the function interfered with ; but this is only attainable by means of the 

 difierent and delicate apparatus of which some portions are above enumerated. 



Another cause often obliges us to renounce vivisection, and to substitute the 

 use of apparatus : it is the necessity of directly studying the human physiology. 

 Of all the beings whose organization and functions science has essayed to inves- 

 tigate, man has been the most frequent object of study. It is the human phy- 

 siology which serves, so to speak, as a type for that of the whole animal 

 kingdom. 



Nevertheless, if it is true that our own organism and functions seem to 

 present the most complete model of animal organization, it is not less true that 

 certain organs, as well as certain functions, are, in us, less sharply characterized 

 than in tiie lower order of beings. Hence it is of the greatest importance to 

 follow, by analysis, each of the phenomena of life in the whole series of living 

 beings, or at least in the principal types, with a view to ascertaining wdiat are 

 the difierent processes which nature em})loys in order to arrive at her end, the 

 life of the individual and of the species. Hence the origin and object of com- 

 parative pJn/siologi/. 



It is to the human being, however, his organs and his functions, that the 

 greater number of investigations is at the present day directed. And, as all 

 resources are to be laid under contribution in the prosecution of our object, we 

 may sometimes borrow aid from the science of medicine, which finds in the study 

 , of maladies certain conditions not always to be realized by experiment. It 

 is not to be forgotten, however, that medicine is not the basis of biology, 

 though, in an ntilitarian point of view-, it may be its end. In such inquiries as 

 we are now pursinng, it is but one means the more of analyzing the conditions 

 which modify the functions of life, and of an-iving at a better determination of 

 the laws which regulate those functions. In order to give an idea of the 

 infiuence which medicine has had on the knowledge of the organism, I need 

 but recall that it was in a case where a perforation of the thoracic walls had 



