PROTOPLASM WALLS OF CAPILLARIES. 285 



told by Strieker himself, that " the finer capillaries 

 consist only of a tube composed of cells or of a 

 cylindrical layer of protoplasm." From such a 

 statement I must dissent, for I have studied, very 

 carefully, the " finer capillaries " in several tissues 

 and organs, and have never seen one in any animal to 

 which such a description could be fairly given. At 

 a very early period of development, of course, 

 capillaries, like all other structures of the body, con- 

 sist of what has been called "protoplasm," but 

 when formed, the wall of the capillaries consists of a 

 material to which the term " protoplasm " cannot be 

 correctly applied. At one time the exigencies of 

 favourite doctrines rendered imperative the discovery 

 of openings in the capillary walls, and the stomata of 

 the fancy were soon developed into "facts." 



Later, however, other philosophical requirements 

 had to be provided for. The walls of the capillaries 

 being protoplasmic, must also be contractile, and 

 Eberth declares that "the capillary wall is contractile," 

 and announces that Strieker saw the capillaries " con- 

 tract to such an extent (!) that not even a single file 

 of blood corpuscles could traverse them," as if he were 

 reporting some new and highly important discovery 

 recently made by that investigator. The fact had 

 been observed by hosts of observers long before 

 Strieker saw the change, though it was explained in 

 a different manner. It seemed hardly necessary to 

 attribute it to the active property of contractility of 

 the capillaries, supposed to reside in the protoplasmic 

 matter, supposed to constitute the wall of the vessels. 

 But Strieker has seen small " looplike projections 

 raise themselves (!) from the wall of the capillaries 

 and again become retracted;" and Eberth remarks 

 that " it is by such contractions the corpuscles are 

 pressed into the capillary wall, and ultimately made 

 to traverse them " (!) So the corpuscles don't make 

 their way through holes in the walls, but are as it 



