286 PROTOFLASM WALLS OF CAPILLARIES. 



were, seized hold of by the contractile protoplasm 

 and pressed through by its contractions. 



The evidence adduced in favour of these doctriaes 

 is most defective — indeed, as regards their application 

 to the phenomena of the capillary vessels of the 

 adult, there is actually no evidence at all. No one 

 has seen the membranous part of the wall of an adult 

 or old capillary vessel contract, while it would be 

 difficult to pick out a tissue less like protoplasm than 

 the transparent material composing the capillary 

 wall. The wall of a fully formed capillary is com- 

 posed neither of irrotopJasm nor hioj)lasm, but it con- 

 sists of a passive membrane permeable to certain 

 aqueoiis solutions. If the thin elastic membrane of 

 the capillary is to be called protoplasm, why should 

 not the posterior elastic lamina of the cornea, or the 

 thin transparent elastic membrane hning an a,rtery be 

 also regarded as of this nature ? But these things, 

 and living growing moving protoplasm (bioplasm) 

 are quite different in their properties. It is indeed 

 difficult to conceive how any one who had really 

 studied the matter, could speak of the oval "nuclei" 

 or bioplasts of the capillary wall and the tissue of 

 the wall itself which intervenes between them, and 

 was formed by them, as being composed of the same 

 substance " protoplasm ;" unless he admitted that 

 this wonderful material might, for example, constitute 

 the moving, changing, semi-fluid sarcode of the 

 amoeba, as well as the firm, passive, unchanging 

 material of which, for instance, the yellow elastic 

 tissue consists. In that case we should be applying 

 the same name to things distinct from one another in 

 their nature and properties. See page 9. 



We shall mislead ourselves and others if we en- 

 deavour to establish resemblances which do not exist 

 in nature, and if we ignore differences which are 

 observable by every one who will simply examine 

 with care and without preconceived theory. If the 



