CAPILLARY CIRCULATION. 



179 



diseases depending upon the presence of disease 

 germs in the blood there is at length unmistakeable 

 evidence of obstruction to the flow of blood through 

 the capillary vessels of different parts of the body,. 

 If this obstruction is incomplete, and only affects a 

 limited area of tissue here and there, the case ter- 

 minates in recovery, but if, on the other hand, the. 

 capillaries of a considerable portion of the body are 

 obstructed, and more especially if the heart's action 

 in such a case should be weak, and the contractions 

 of the left ventricle not sufficient to drive the blood 

 forcibly towards those capillaries which may yet 

 remain more or less pervious, the disease must be fatal, 

 and probably during its early stage. It is therefore 

 of the utmost importance in critical cases to excite 

 the heart's action by giving remedies which are known 

 to have this effect. See also page 140. 



The contagious disease germs in some instances, 

 as has been already suggested, are perhaps enveloped 

 in a coagulum of fibrin, and thus are formed little 

 masses which would be too large to traverse the capil- 

 lary vessels. Mr. Lee showed that if pus. was injected 

 into the blood of a living animal, coagulation of the 

 fibrin of the blood immediately occurred. In the case 

 of some contagious disease germs, it is possible that 

 the coagulation of fibrin around the contagious par- 

 ticles may only increase the size to that of a white 

 blood-corpuscle, or little larger, but a body even of 

 this size would, under some circumstances, fail to pass, 



