54 BIOLOGY. [Book i. 



on the one hand from the tissues, and on the other from the 

 exterior medium 1 But these tissues constantly grow larger from 

 birth to the adult state or age, that is to say, that incessantly 

 during this lapse of time new elements arise and gain place in 

 the midst of the old. Evidently these elements are formed at 

 'the expense of the interstitial liquid, which consequently then 

 becomes a true formative blastema. 



Let a freshwater polypus be sectioaised into several frag- 

 ments : immediately each of these fragments strives to complete 

 itself, strives to remake a complete individual; but this new in- 

 dividual once formed is not more voluminous than the fragment 

 whence it took its bix-th. It has therefore modelled and consti- 

 tuted itself at the expense of the interstitial liquid, bathing the 

 cellular tissue* of the hydra ; therefore this liquid is formative ; 

 therefore it is a blastema. But blastema is likewise the inter- 

 cellulary liquid of the grey cerebral substance, that of the umbili- 

 cal cord, that of the marrow of the bones, and so on. 



The chemical composition of the animal blastemas is a little 

 better known than that of the vegetal blastemas. Like these 

 last, they are composed of albuminoidal substances, of salts, and 

 of regressive crystalloidal substances ; lastly, of a great quantity 

 of water. But besides these general characteristics it has been 

 successfully demonstrated that the blastemas of the superior 

 animals have a composition different from that of the blood and 

 the lymph, from which chiefly they are derived. They possess 

 fibrine and albumine in smaller quantity. Largely albumine 

 takes in them its chemical, soluble, and assimilable form ; it be- 

 comes albuminose, no longer coagulates from heat, and coagulates 

 imperfectly and with difficulty through the acids. Pibrine is no 

 longer found therein, and nothing is more natural, for we know 

 that to become assimilable, nutritive, fibrine needs to be trans- 

 formed isomerioally into albuminose. 



There has been a desire to make of the chemical instability of 

 the blastemas a distinctive characteristic. No doubt the blaste- 

 mas are in a state of perpetual mutation ; they are never iden- 



