THE AMEBIC AN NATURALIST [Vol. LIV 



It might at first be supposed that the same argument 

 would justify the placing of cerebral hemorrhage with 

 the circulatory system in the primary organological 

 classification, but this does not seem to be warranted. 

 From an organological point of view the brain must be 

 considered as a ivhole organ, the machinery of its vascu- 

 lar supply being included as well as its proper nervous 

 components. So in this respect cerebral hemorrhage 

 properly belongs where it is placed in Table VII, with 

 the nervous system. 



But the case is different from the embryological view- 

 point. Suppose it be granted for the moment that there 

 are specific differences between tissues originating from 

 the different germ layers in respect of their likelihood 

 to break down functionally under strain. Then clearly the 

 tendency to any such specificity would be obscured if we 

 charged to ectoderm the breakdown of any organ pri- 

 marily originating from that germ layer, but where in 

 fact the initial cause of the functional stopping of the 

 proper ectodermic tissue was the prior breakdown of a 

 part of the organ which was mesodermic in origin. This 

 is precisely the condition of affairs relative to the 

 pathology of cerebral hemorrhage. 



Again, softening of the brain is really a necrosis of 

 brain tissue resulting from a cutting off of its nourish- 

 ment by stoppage of the circulation, which in turn may 

 be due to arthritis, thrombosis, embolism or pressure. 

 The same reasoning applies here as in the case of cere- 

 bral hemorrhage. 



In so complicated a matter as the distribution of causes 

 of death to their embryological base probably the most 

 that can ever be hoped for, having regard to the enor- 

 mous complications of structural development, is to get 

 limiting values, within the range comprehended by which, 

 the true fact may be reasonably supposed to lie. To this 

 end Table XIII has been constructed. It with Table XII 

 gives lower and upper limiting values 'for death rates 

 chargeable to ectoderm and mesoderm. Table XIII is 



