NUCLEI, OK BIOPLASTS OF CAPILLARIES. 287 



oval nuclei are protoplasm, and the membranous wall 

 is protoplasm, the student will, of course, ask us how 

 we account for the important differences between these 

 two things, and then we shall be driven to resort to 

 the unfortunate expedient of suggesting that one is 

 protoplasm, and the other is "changed" protoplasm. 

 296. Nuclei, or masses of bioplasm of caiiillaries. 

 — More or less connected with the wall of the capil- 

 lary vessel are numerous bioplasts consisting of 

 living matter or bioplasm, which vary greatly in 

 number in the capillaries of different tissues. Of 

 these there are at least four distinct sets which may 

 be distinguished in well-prepared specimens. 



1. Those in the capillary wall itself, which have 

 taken part in its formation, and which are intimately 

 concerned in nutrition as long as blood circulates 

 through the vessel. These vary greatly in number 

 in different capillaries, as represented in many of my 

 drawings, and in size also at different times. In 

 some specimens they are extremely numerous, and, 

 as I pointed out in 1863, project into the interior of 

 the capillary vessel. Probably from these are de- 

 tached particles of bioplasm, which pass into the 

 blood cturent. and may grow into white blood cor- 

 puscles. These bioplasts are represented in Fio-. 2, 

 pi. XV, and in figs. 1, 2, 3, pi. XVI. 



2. Masses of bioplasm outside, but at a varying 

 distance from the capillary wall with which they are 

 connected by extensions or processes. These have 

 no doubt originated from the first by fission, and are 

 indeed an early stage in the formation of new capil- 

 laries, as may be proved by examination of the 

 capillaries of adipose and some other tissues which 

 undergo great and rapid changes even in the adult. 



3. Oval masses of bioplasm, generally, but not in- 

 variably, smaller than the above, and, unlike them, 

 sometimes crossing the vessel obliquely. These are 

 connected with the delicate nerve fibres distidbuted 



