1YO LECTURE VII. 



one, just as connective tissue originally wears the form 

 of a homogeneous intercellular substance (mucus) from 

 which fibres are only by degrees, if I may so express 

 myself, excreted, or, to employ the usual term, differen- 

 tiated. So fibririe, too, which is first of all gelatinous, 

 becomes differentiated into a fibrillar mass. And indeed 

 in the case of inorganic substances also we find certain 

 analogous appearances. From deposits of calcareous 

 salts or silicic acid, which were originally perfectly gela- 

 tinous and amorphous, solid granules and crystals are 

 gradually separated. 



The name fibrils may therefore still be retained to 

 designate the usual form in which fibrine presents itself, 

 but at the same time it must be borne in mind, that this 

 substance originally existed in a homogeneous, amor- 

 phous, gelatinous condition, and can again be reduced 

 to it. This reduction can not only be effected artificially, 

 but takes place also naturally in the body itself, so that 

 where we have previously found fibrils, we may after- 

 wards meet with the fibrine in a homogeneous condi- 

 tion, as, for example, in the vessels, where aneurysmal 

 coagula, and others, are gradually converted into a 

 homogeneous mass of cartilaginous density. 



Now, with reference to the second portion of the 

 blood, the blood-corpuscles, I may express myself briefly, 

 as they are well-known elements. I have already 

 remarked that nearly all the histologists of the present 

 FlG 51 time are agreed that the co- 



c loured corpuscles of the blood 



d^af f man an d the higher mam- 



/\N^ ^^ 



Q rnalia contain no nuclei, but 

 that they are simple vesicles, 



Fig. 51. Nucleated blood-corpuscles from a human foetus, six weeks old. 

 a. Homogeneous cells varying in size, with simple, relatively large nuclei, of which 



