598 



the vesicular structure of the corpuscles but is inexplicable on the 

 stroma theory. 



With regard to the physical condition of the membrane, observ- 

 ations upon the fresh corpuscles show that it cannot be solid but must 

 be soft and almost fluid; probably nearly resembling mucus in con- 

 sistence. This is quite obvious from the manner in which the cor- 

 puscles are mechanically distorted; as is often seen in their passage 

 along the capillaries, and also very strikingly wher currents are pro- 

 duced through a microscopic preparation of blood. Under these circum- 

 stances it frequently happens that a corpuscle here and there sticks 

 at one place to the glass and is not carried along with the rest by the 

 stream of fluid. Such corpuscles are apt to be drawn out into a tail 

 by the current, the corpuscle instantly resuming its normal shape when 

 the flow ceases or if the fixed part becomes detached from the glass. 

 This phenomenon may be observed both with the mammalian and the 

 amphibian corpuscle and is conclusive as to the physical condition of 

 the envelope. 



Conclusions. 



1. The erythrocyte, both in mammals and in oviparous vertebrates, 

 is a vesicle consisting of a thin membrane enclosing fluid contents. 

 The vesicular structure is proved by 



a) the action of water and solutions of electrolytes, with which 

 the corpuscle behaves exactly as would be the case if it were en- 

 closed by a semipermeable membrane; 



b) the result of mechanical injuries and of strong electric shocks, 

 which cause rupture of the envelope and escape of the fluid contents; 



c) the invagination of the edge of the corpuscle which occurs 

 when a relatively large flagellated organism such as a trypanosoma 

 impinges against it; 



d) the fact that it can be sharply and distinctively stained by 

 methyl violet and certain other basic dyes; 



e) direct observation of the fresh amphibian erythrocyte, which 

 frequently exhibits folds and wrinkles of the investing membrane; 



f) the fact that the nucleus of the amphibian erythrocyte is easily 

 displaced from its central position, which could not happen were 

 it imbedded in a "stroma". 



2. The membrane of the erythrocyte is composed of a soft, yielding, 

 elastic material, mucus-like in consistence and chemically resembling 

 protoplasm ; containing nucleo-proteids, lecithin and Cholesterin in al- 

 most the same relative amount as protoplasm. The presence of these 

 two "myelin" substances, which in many of their physical characters 



