26 SNAKE-POISON AND ITS ACTION. 



puscles force their way out of the vessels through 

 pores in the cement substance, since a passage of cell 

 through cell is not thinkable. Thus far we see 

 our way fairly clear. But the question now arises : 

 what causes the solid constituents of the blood 

 to force their way through the capillary membranes all 

 over the mucous surfaces, even the conjunctiva, and not 

 these alone, but also through serous membranes such 

 as the pericardium, and strangest of all, through old 

 scars in the skin ? If the most modern ideas as to 

 the cause of diapedesis being blood pressure are 

 correct, it is quite incomprehensible how it can take 

 place in the absence of blood pressure, and take place 

 so extensively. The theory of blood pressure may 

 apply to diapedesis' accompanying the inflammatory 

 process. In snakebite poisoning it is more likely to 

 be due to passive engorgement of the capillary system 

 and probably also to blockage of corpuscles in the finest 

 capillary tubes. In vaso-motor paresis, and still more 

 paralysis, the arterioles supplying the capillaries are 

 widely dilated, and at the lowest blood pressure pro- 

 bably send more blood into the latter than in the normal 

 state. This circumstance in itself is apt to cause 

 capillary engorgement. In the finest capillaries per- 

 mitting only a string of corpuscles, one behind the other 

 but none abreast, to pass through in the normal state, 

 dilatation may cause blockage by two or three becoming 

 wedged in abreast and closing the lumen of the vessel 

 by a sort of embolism. On the arterial side of this 

 obstruction the crowded corpuscles force their way 



