52 Transactions of the 



I must, for tlie sake of explanation as to the cause of this differ- 

 ence, allow myself to offer some remarks regarding the behaviour 

 of fully-developed blood corpuscles in reference to external influ- 

 ences. These also involve, to some extent, the question regarding 

 the existence or non-existence of an enveloping membrane of these 

 bodies. 



In examining fresh and fully-developed human blood corpuscles 

 in their natural liquid, the liquor sanguinis, it is impossible to 

 discover a distinct trace of an enveloping membrane upon them ; 

 but, in treating them with pure water, they soon become colourless 

 by parting with their colouring matter, and apparently disappear 

 from view. By a still closer examination, however, and with a 

 first-class objective, they are to be seen in the form of very delicate 

 small vesicles, bounded by a fine double contour. By the escape 

 of their contents through the endosmosis of the water they have 

 somewhat shrunken, and, in consequence, become smaller in 

 diameter. Some of them have lost their bi concavity, and been 

 rendered biconvex, or even spherical, while others have retained 

 the shape they possessed before the application of the water, either 

 biconcave, cup-shaped, or even crenated. All, however, without 

 regard to their form, show the dehcate double contour. In this 

 condition the blood corpuscles are much inclined to congregate in 

 groups adhering to each other. In some instances where a number 

 of corpuscles have, by mutual pressure, assumed a hexagonal form, 

 as it frequently occurs, this is retained after the treatment with 

 water, and, by virtue of the double contour which they now show, 

 the whole group appears almost as a layer of pavement-epithelium. 

 More rapidly still than water, acts a weak solution of chromic acid. 

 As soon as a drop of this is brought under the covering glass, the 

 double contour appears, and sharper even than in the preceding 

 case. If the solution is sufficiently strong, it then coagulates the 

 liquor sanguinis in a granular and fibrillar form. In this case 

 the blood corpuscles lose their own colour, but appeax tinted by the 

 chromic acid. If the solution is very weak, they will then appear 

 in the form of well-defined and clear double-contoured vesicles. 

 Treated with a solution of chromic acid, they lose but little of their 

 diameter. When coloured blood corpuscles are exposed for some 

 time to the action of the gastric juice — as it occurs in yellow fever, 

 where considerable extravasations from the smaller blood-vessels of 

 the stomach take place, to be finally ejected in the form of black 

 vomit — the same changes, with a still greater loss of diameter, are 

 observed. 



The behaviour of coloured blood corpuscles in relation to 

 external influences is not always the same during different periods 

 of their development and course of life. Thus, for instance, are 

 the larger and older corpuscles of human embryos changed into 



