158 CAPILLARY VESSELS. 



lowish-red colour. Notwithstanding repeated endeavours, I 

 cannot succeed at this season of the year when the hens are 

 moulting, in subjecting eggs to incubation for so long a period, 

 I can, therefore, only give a representation of these vessels 

 from a recollection of what I observed in the early part of 

 this year. (See pi. IV, fig. 12.) In some situations the capil- 

 laries are perfect, and connected with the larger vessels ; at 

 others they have the appearance represented in the figure, and 

 illustrated previously by observations on the tail of the tadpole. 

 In addition to these capillaries, which form a network of 

 canals of irregular caliber and give off blind branches, some 

 separate irregular corpuscles are seen, such as h and i, which 

 do not appear to be connected with the vascular network. 

 These bodies send off blind processes of various forms in 

 different directions, and have the appearance, therefore, of 

 stellate cells. They have a yellowish-red colour, like that of 

 the bone-capillaries, which circumstance is alone sufficient to 

 suggest the supposition that they are cells of capillary vessels 

 in progress of development. This becomes much more pro- 

 bable, when we observe some of these corpuscles, such as k, 

 already connected with the true capillaries. We may, there- 

 fore, with a high degree of probability at least, regard them 

 as the primary cells of capillary vessels ; and in that case the 

 description of the formation of these vessels, previously given, 

 would be the correct one. The following would, therefore, be 

 the mode in which the formation of the capillaries and of the 

 blood takes place in the germinal membrane : among the 

 cells which compose the germinal membrane, some which are 

 deposited at certain distances from one another, are deve- 

 loped into the primary cells of capillary vessels by becoming 

 elongated on different sides so as to form stellate cells. 

 The processes of the different cells come into contact and 

 coalesce, the septa are absorbed, and in this manner a network 

 of canals of very irregular caliber is produced, the prolonga- 

 tions of the primary cells being much thinner than the bodies 

 of the cells. These processes of the cells or passages of com- 

 munication undergo expansion until they and the bodies of 

 the cells all attain one equal width, until, in fact, a network of 

 canals of uniform caliber is formed. The fluid portion of the 



