MODERN BIOLOGY 361 



lar-tissue theories of his predecessors, Caspar Friedrich WolfF and Bichat, it 

 represents an undoubted advance; it is one of many examples of how knowl- 

 edge in a given sphere progresses, as it were, fumblingly from generation to 

 generation until, finally, the decisive word has been spoken. In regard to the 

 conception of tissues and the part they play in the formation of the organs, 

 Blainville otherwise associates himself closely with Bichat, and he likewise 

 adopts the latter's theory of organic and animal life, which, however, he 

 employs with considerably greater moderation than its creator. For the rest, 

 he believes a living body to be a kind of chemical workshop wherein fresh 

 molecules are constantly being conveyed and old ones removed, where the 

 combination is never fixed, but always, so to speak, "in nisu," resulting in 

 constant motion and heat. This view of life is certainly not vitalistic, but 

 Blainville nevertheless emphasizes in what follows the contrast betwxen 

 "general" and "vital" forces, both unknown as to their real nature, but the 

 former far more measurable than the latter; both operate in the living body 

 and life's intensity is dependent upon the ascendancy of the life-forces over 

 the general forces. In this sphere, then, Blainville wavers somewhat between 

 divergent principles, and on the whole he has been counted amongst the 

 vitalists. The two primary qualities of life are, according to him, "cowpo- 

 sition" and " dkom-position" ; in the former is included the absorption of 

 nourishment, in the latter not only excretion, but also reproduction. Among 

 the alimental organs are also counted the organs of motion and, in general, 

 everything that moves the external bodily form, to which Blainville as- 

 cribes a fundamental importance for all knowledge of animal life. His sys- 

 tem rests entirely on this basis and thereby acquires a somewhat artificial 

 character; nevertheless, it has done considerable service, chiefly in the fact 

 that here for the first time a definite line of demarcation is drawn between 

 amphibians and reptiles, which all subsequent research has confirmed. For 

 the purposes of his special presentation of comparative anatomy Blainville 

 prefers to go from the higher form to the lower, his arguments in justifica- 

 tion of which are somewhat reminiscent of Lamarck's "degradation" theory. 

 In other respects, too, his treatment of comparative anatomy is based on a 

 form of theoretical speculation that renders the actual method of presenting 

 his subject highly artificial; it would, however, take too long to go more 

 deeply into these questions. Undoubtedly Blainville's works contain, besides 

 much that is absurd, a number of ideas of immense value, both in detail and 

 as a whole. Among these may be specially mentioned the importance he at- 

 taches to the stages of embryologic development as a basis of comparison 

 between the animal forms, a principle that, as is well known, has since 

 proved of fundamental importance to comparative anatomy. For this fact 

 science has to thank a number of works in the sphere of embryology that 

 were brought out during the period now under discussion. To this sphere, 

 therefore, we shall now proceed. 



