408 NOTES AND MEMORANDA. 



clot may however be always found, although often obscured 

 by the liberated corpuscles. Now, this disappearance of the 

 clot of frog's blood under certain circumstances was noticed 

 some years ago by v. Recklinghausen, and ascribed by him 

 to a reliquefaction of the fibrin ; and not unnaturally, if we 

 consider the astonishing diminution in bulk which it under- 

 goes, and the fact that the serum in such cases is frequently 

 found to yield a further coagulum. 



But in every case of the latter kind, i. e. in every case in 

 which the supernatant fluid yields a coagulum in a capillary 

 tube, it will have been found that the primary coagulation 

 Avas incomplete, i. e. that the central parts of the blood re- 

 mained fluid, whereas on the other hand it is certain that 

 when the primary coagulation has been complete, no further 

 coagulum is ever obtainable, although, in this case also, the 

 clot may have contracted, to a relatively exceedingly small 

 bulk, in fact, may have almost disappeared. 



A further proof, if one were needed, that the diminution 

 of the clot is due merely to contraction and not relique- 

 faction of fibrin is to be found in the examination under the 

 microscope, using an immersion objective, of the process as 

 it occurs in a very thin-Avalled and fine capillary glass tube. 



The phenomena here observed are wholly those of con- 

 traction, first simj^ly serum, then white corpuscles, and 

 finally red corpuscles being expressed, until a mere thread 

 of fibrin remains, almost obscured by -the corpuscles and 

 still including a few. 



Throughout the Avhole process, however, there is no trace 

 of a reliquefaction of fibrin; this Avould of course involve 

 the dropping away of the corpuscles from the sides : on the 

 contrary, they are most evidently squeezed out, some of 

 them being actually ruptured in the passage and appearing 

 on the exterior of the clot as small reddish spheroids. The 

 facts then, briefly, are these : that frog's blood, especially if 

 taken during the winter months, exhibits but very little 

 tendency to coagulate, with the exception of the portion in 

 immediate contact with a foreign surface ; that, when ap- 

 parently coagulated throughout, the central portions are 

 very apt to remain fluid, and to impart coagulability to the 

 expressed serum ; that the clot when formed frequently 

 tends to attain a relatively very small bulk; and, finally, 

 that this diminution in bulk is due to contraction merely, 

 not reliquefaction of the fibrin. 



