BICHAT 27 



Quadrupeds, Cetacea, birds, amphibians and fish are as 

 unlike as possible in external form and in the shape of their 

 limbs ; but they all resemble one another in their internal 

 organs. Let the internal organs change, however the ex- 

 ternal parts will change infinitely more, and you will get 

 another animal, an animal of a totally different nature. 

 Thus an insect has a most singular internal economy, and, 

 in consequence, you find it is in every point different from 

 any vertebrate animal. 



In this contrast, on the whole justified, between the 

 importance of variations in the " vegetative " and variations 

 in the "animal" parts, one may see without doing violence 

 to Buffon's thought, an indication of the difference between 

 homology and analogy. It is usually in the external parts, 

 in the organs by which the animal adapts itself to its 

 environment, that one meets with the greatest number of 

 analogical resemblances. This contrast of vegetative and 

 animal parts and their relative importance for the discovery 

 of affinities was at any rate a considerable step towards an 

 analysis of the concept of unity of plan. 



To Xavier Bichat (1771-1802) belongs the credit of work- 

 ing out in detail the distinction drawn by Aristotle and Buffon 

 between the animal and the vegetative functions. Bichat 

 was not a comparative anatomist ; his interest lay in human 

 anatomy, normal and pathological. So his views are drawn 

 chiefly from the consideration of human structure. 



He classifies functions into those relating to the individual 

 and those relating to the species. The functions pertaining 

 to the individual may be divided into those of the animal 

 and those of the organic life. 1 " I call animal life that order 

 of functions which connects us with surrounding bodies ; 

 signifying thereby that this order belongs only to animals" 

 (p. Ixxviii.). Its organs are the afferent and efferent nerves, 

 the brain, the sense-organs" and the voluntary muscles ; the 

 brain is its central organ. " Digestion, circulation, respira- 

 tion, exhalation, absorption, secretion, nutrition, calorification, 

 or production of animal heat, compose organic life, whose 

 principal and central organ is the heart " (p. Ixxix.). 



The contrast of the animal and the organic life runs 

 1 Anatomic Generate, Paris, 1801, Eng. trans. 1824. 



