Circulation of the Blood. 185 



two atmospheres ; and the same facts were observed even in 

 the case of gases. Thus sulphurous acid gas would pass 

 through a piece of India rubber against a pressure of seven 

 and one-third atmospheres; carbonic acid against a pressure 

 of ten atmospheres; and sulphuretted hydrogen, though re- 

 sisted by more than twenty-four atmospheres. 



Explanatory Remarks on the Coagulation of the Blood. — 

 When blood recently drawn is kept in a vessel for a space of 

 time it spontaneously separates into two well-defined portions, 

 the one liquid and the other a soft solid — the serum and the 

 clot. 



Physicians generally regard this as due to the death of the 

 blood. Whilst it is in the system it is under the influence of 

 the vital force; but when removed it spontaneously undergoes 

 the change in question, and, unable to keep its primitive con- 

 dition, coagulates and dies. Accordingly this partial solidifi- 

 cation of the blood is looked upon as a mysterious phenome- 

 non, and though from time to time many experiments have 

 been made and explanations offered, that which refers it to 

 the presence or absence of the vital principle appears to be 

 most generally received. 



But it is very doubtful whether any such special power as 

 a vital force exists. In the instance under consideration I 

 cannot comprehend how a loss of vitality in the blood can in 

 any manner elucidate or indeed have anything to do with the 

 fact of its coagulation. 



It appears to me that what occurs to the blood when drawn 

 is precisely the same as that which occurs to it continually 

 when in the system. If its fibrine coagulates in the receiving 

 cup, it tends equally so to do in the peripheral circulation. I 

 can see no difference in the two cases. And if this be true, 

 it obviously is a fruitless affair to be seeking for an explana- 

 tion of a difference in habitudes in and out of the system, 

 when those differences in reality have no existence in nature. 

 If, when blood flows into a cup, we could by any mechanism 

 withdraw the particles of fibrine as they agglutinate together, 

 the phsenomenon of coagulation would never be witnessed ; 

 and this is precisely the result in the living mechanism. The 

 fibrine, as it passes into the proper condition, is removed by 

 a series of events which will be hereafter explained. But 

 whether it be in those states which physiologists designate 

 living or dead, it exhibits continually the same tendency. 



When we remember that the average amount of fibrine in 

 blood scarcely exceeds one-five-hundredth part of its weight, 

 and that this minute quantity is sufficient, by entangling the 

 blood-discs, to furnish so voluminous a clot, we have little 



