604, [June 11, 



it would be unable to produce such an effect at all. This appears to 

 me to be very interesting physiologically, but especially so with 

 reference to pathology. I must not go now fully into the circum- 

 stances that lead me to it ; but I may express the opinion I have 

 formed, that clot must be regarded as living tissue in its relation to 

 the blood. It is no doubt a very peculiar form of tissue, in this 

 respect, that it is soft, easily lacerable, and easily impaired in its 

 vital properties. If disturbed, as in an aneurism, it will readily be 

 brought into that condition which leads to the deposition of more 

 clot ; but if undisturbed, it not only fails to induce further coagula- 

 tion, but seems to undergo spontaneous organization. I have seen a 

 clot in the right side of the heart, and extending into the pulmonary 

 artery and its branches, unconnected with the lining membrane of 

 auricle or ventricle or with the pulmonary artery except at one small 

 spot where it had a slight adhesion, developed into perfect fibrous 

 tissue by virtue, it would appear, of its own inherent properties. 

 Another observation which I once made, and which then completely 

 puzzled me, now seems capable of explanation. In laying open the 

 blood-vessels- of a dead body, I observed in many of the veins a deli- 

 cate white lace-like tissue which evidently must have been formed 

 from a clot. This I now believe to have had the same relation to 

 the coagulum as the flimsy cellular tissue of old adhesions has 

 to lymph. 



It may not be altogether superfluous to mention some other facts 

 illustrative of the active influence of ordinary matter in promoting 

 coagulation, and the negative character of the lining membrane of 

 the vessels. I find that a needle introduced into one of the veins of 

 the foot of a sheep for a much shorter time than is necessary to pro- 

 duce the first appearance of the actual deposit of fibrin upon it, leads 

 after a while to coagulation where the needle had lain in other 

 words, that a foreign solid, by a short period of action on the blood, 

 brings about a change that results in coagulation, though the blood 

 still lies in the living vessels. I have also ascertained that after 

 blood has been made to coagulate in a particular vessel by introducing 

 a needle into it, if the coagulum as well as needle is removed, and 

 more fluid blood is allowed to pass in, this blood remains fluid for an 

 indefinite period, showing that the needle had not impaired the pro- 

 perties of the vessel by its presence ; so that the previous coagulation 



