CHAPTER IT. 



OP THE GENERAL CONDITIONS OF GROWTH. 



GROWTH is essentially the result of the predominance of assimi- 

 ilation over disassimilation, that is to say, it cannot be effected 

 'without the concurrence, the immediate presence of a sufficient 



provision of assimilable materials. But the living anatomical 

 ; elements seem sometimes capable of profoundly modifying and 



metamorphosing these materials in a great degree. According 



to M. Cl. Bernard, the larvae of flies form their organised 

 {tissues from substances soluble in alcohol, and consequently 



deprived of albuminoidal substances, properly so called. Not- 

 I withstanding, as a general rule, a certain analogy of chemical 



construction is necessary between the different kinds of histo- 

 1 logical elements and the blastemas, at the expense of which 

 f i these elements live and develop themselves. If, for example, 

 8 we transplant, by animal grafting, the anatomical elements of 

 |one animal to another, the operation will be likely to succeed 

 'in proportion as the animal species are analogous. 



As to the general conditions of heat, light, oxygenation, and 

 ; alimentation, we must refer to the chapters treating of nutrition, 

 and limit ourselves to pointing out the particular facts relating 

 directly to growth itself. 



It has been pretended that certain animals, certain tissues, can 

 [live and develop themselves without oxygen. These paradoxical 

 if acts must only be received with extreme reserve. They have, 

 ! without doubt, been insufficiently observed, badly elucidated, and 



are included probably in the general law, according to wliich 



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