6 Transactions of the 



pliilosopliical answer to give is " variously." This we shall find 

 perfectly convincing, and not followed by any further troublesome 

 inquiries concerning the nature of the physical nuclei or basis of 

 capillaries. 



Nuclei, or Masses of Bioplasm of Cainllaries. 



More or less connected with the wall of the capillary vessel are 

 numerous " nuclei," 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 draw- 

 ings, 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 

 detached particles of bioplasm, which pass into the blood cui'rent 

 and may grow into white blood corpuscles. 



2. Classes 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 

 capillaries, 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 invariably, 

 smaller than the above, and, unlike them, sometimes crossing the 

 vessel obhquely. These are connected with the delicate nerve 

 fibres distributed to the capillary vessels. In some cases these 

 bioplasts, as well as the fine nerve fibres connected with them, are 

 almost embedded in the wall of the capillary, but oftentimes they 

 are seen to be separated from it by a distinct interval, which varies 

 much in extent, as is well demonstrated in some of my specimens. 



4. Elongated and stellate masses of bioplasm which belong to 

 the connective tissue. These vary greatly in number, size, and 

 appearance in different tissues. 



Nerve Fibres. 



I have demonstrated that nerve fibres are distributed to capil- 

 lary vessels in almost all the tissues of the frog and newt. Among 

 these I would particularly mention the skin and mucous memlranes, 

 the capillaries of the lung and kidney, those of the pericardium 

 and fibrous membrane near the liver, and those of the mesentery, 

 as well as the capillaries of muscle and 7ierve. 



