30 THE TONER LECTURES. 



(liffeient periods, and that there has been a succession of de- 

 positions from below upward, so that the bottom portion has 

 been first and tlie top last formed. While speaking of the 

 differences shown by tlie several portions of this fibrinous or 

 blood coagulum, it may be Avell to mention that there is still a 

 further want of homogeneity besides that for which a mere 

 difference in age will account. 



The three lower portions of this blood-clot, aside from 

 changes due to differences of age, have a similar structure ; 

 their elements are similarly' arranged. But the fourth portion, 

 constituting the apex of the clot, is, respecting the arrange- 

 ment of its elements, of very different constitution; but more 

 of the peculiaritj' of this portion anon. 



What now follows has I'eference only to the three lower por- 

 tions of the blood-clot. As has been already remarked, each of 

 the lower portions aiJi)ears to have been similarly constituted. 

 Their similarity in constitution appears to indicate that they 

 have been formed in a similar manner. A detailed description 

 of one of them will suffice for all. Each of the three lower 

 portions itself appeared, at first glance, to be formed of from 

 two to four or more strata, successively and interruptedly 

 superimposed. But a more careful examination under a higher 

 power proved that the edge of a stratum could be traced in an 

 uninterrupted serpentine course from the bottom to the top of 

 the portion. Still closer inspection demonstrated the existence 

 of another unexpected phenomenon, viz., the middle portion or 

 line of such a serpentine stratum was composed almost entirely 

 of red lilood-corpuscles, a very few white ones being intermin- 

 gled, while the borders of the stratum were mainly composed 

 of a network of bands of fil)rin whose prevalent direction was 

 paralU'l with that of the middle line of the stratum. In the 

 meshes of this fibrinous reticulum wero numberless white blood- 

 corpuscles and a few red ones. Tiie serpentine course of the 

 stratum was such that between the lateral bends the border 



