440 



EDWARD HORNE CRAIGIE 



OBSERVATIONS 



The thickness of the sections was such that the complete 

 capillary mesh did not show, the vessels appearing as short pieces, 

 which were much more easily measured than they would have 

 been if they had formed complete meshes within the field. That 

 this appearance was due only to the thinness of the sections may 

 be seen by comparing figures 1, 2, and 3, which represent parts 

 of sections 20 n thick, with figure 4, which represents part of a 

 50 n section and figure 5, which is from one considerably thicker. 

 The complete spongy mesh is not illustrated in the figures, as 

 it was found impracticable to project satisfactorily upon one 

 plane the complex system of capillaries seen in a section thick 

 enough to show this, the course of the vessels being much con- 

 torted. Enough is represented, however, to indicate that such 

 a condition actually exists, and one complete mesh appears in 

 figure 5. The figures 1 to 3 were drawn with the aid of a Leitz- 

 Edinger projecting microscope, while an ordinary microscope 

 was used for projection in the preparation of figure 4 and figure 

 5. The illustrations show clearly the evident difference in 

 vascular richness of the regions represented. In figure 1 and 

 figure 2 the more conspicuous cell bodies are indicated in gray 

 to show their relation to the vessels. Nowhere were the meshes 

 of the capillary net small enough to surround single cells, as 

 described by Rudanowsky, nor were there any traces of a delicate 

 secondary network filling the primary meshes (Adamkiewicz, 

 loc. cit.). The smallest meshes noticed were about 80 /x in 

 diameter, but no study of this matter was made, as the contorted 

 course of the vessels caused such measurements to be practically 

 useless, besides preventing a complete loop from lying in one 

 section unless this was very thick. 



