THE BLOOD-VESSELS. 



147 



D, 



corpuscles which are comparatively narrow, the larger vessels 

 having broader cells. In man they have an average length of 

 0.07560.0977 mm., and an average breadth of 0.010.05 mm. 

 The intercellular boundaries, brought out as dark lines by 

 means of the silver salt, frequently exhibit little nodular swell- 

 ings. (See Fig. 58.) 



In addition to the ordinary endothelia, we find smaller 

 areas, generally without nuclei ; they have rounded or some- 

 what dentate contours, 

 and are interposed be- 

 tween the other cells. 

 Eberth believes that 

 some of these intercal- 

 ated areas, as Auerbach 

 has called them, proba- 

 bly correspond to por- 

 tions of strangulated vas- 

 cular cells. It is more 

 logical to regard them as 

 the remnants of an in- 

 complete endothelial des- 

 quamation, a process 

 which is of physiologi- 

 cal occurrence through- 

 out the blood-vessels. 

 These remaining bits are 

 finally destined to be- 

 come quite detached 

 from the vascular wall, and are then swept away by the rush 

 and flow of the blood-current. The detached portions of such 

 endothelia and their nuclei appear as free granules in the blood, 

 where they have puzzled many observers, and have been vari- 

 ously called microcytes, hcematoblasts, etc. From this descrip- 

 tion it is plain that Cohnheim's view, that these spaces are 

 openings or stomata, is not sustained. True, we find in serous 

 membranes of certain animals real openings, but these always 

 appear of rounded shape, and are, to say the least, not com- 

 monly observed in human blood-vessels. This statement of 

 the case does not militate against Cohnheim's well-known 

 views that the corpuscles emigrate through the vessels, for, 

 remembering the protoplasmic nature of the endothelial tubes, 



FIG. 61. A,A, stellate connective-tissue cells connected by 

 B,B, delicate protoplasmic threads to C,C, sprouts of endothe- 

 lial tubes ; D, protoplasm connecting two capillaries ; E, nu- 

 cleus imbedded in a primitive sprout of protoplasm, budding 

 from wall of capillary. Specimen prepared by silver nitrate. 



