600 SPECIAL HISTOLOGY. 



under acetic acid the contents, together with the cell-membrane, are 

 rendered pale, and soon dissolve ; whilst the nuclei at the same time 

 soon become pale, and finally, on the application of caustic alkalies, 

 disappear in the same manner as the membrane. Besides these gra- 

 nules, which I do not hesitate to declare are a protein substance, and 

 the albumen in solution in the contents, the cells very commonly contain 

 some dark oil-drops, and more rarely one or another, exhibits granules 

 of yellow pigment. 



The straight and convoluted canals, together with the general cha- 

 racters just described, present some differences. The former, although 

 originally of the considerable width of even 0-06-0-1 of a line, soon 

 diminish, in consequence of the divisions they undergo, to a diameter of 

 0-01-0-014-0-018 of a line, but in the " bundles of Ferrein," again 

 acquire the size of 0-02-0-24 of a line. With this diameter they enter 

 the cortical substance, but subsequently, in the proper convoluted 

 tubules, attain one of 0-033 of a line, though again somewhat constricted 

 close to their commencement. The membrana jiropria in the convoluted 

 tubules is more delicate (0-0003-0-0004 of a line) and isolated with 

 more difficulty, the epithelium, on the contrary, is usually thicker, with 

 cells measuring 0-008-0-012 of a line in width, and 0-004-0-005 of a 

 line in thickness; whilst in the straight tubules the cells are not more 

 than 0'004-0-006 of a line wide, and 0*004 of a line thick. Physiolo- 

 gically, it also seems to me worthy of remark, that the last cells have 

 clear, non-granular contents, whence, also, the medullary substance, in 

 the bloodless condition, appears whitish, whilst the cortical exhibits a 

 yellowish hue. 



The Malpighian bodies present a very peculiar structure. They are 

 to be regarded as appendages of the convoluted tuhiili uriniferi, and 

 contain imbedded in their epithelium, and, as it may be said, entirely 

 filling their cavity, a compact, rounded vascular plexus — the glomerulus 

 I\Ialpighianus, the structure of which will be afterwards described. The 

 same membrana propria, which surrounds the tuhuli uriniferi, also 

 somewhat thickened (0-0005-0-0008 of a line) invests these bodies (Fig. 

 247 a); and the epithelium is likewise continued into the capsules thus 

 formed, only that its cells are smaller and less distinct, and invest the 

 vascular coil on the side directed towards the canal of the emergent 

 [tubulus uriniferus. This latter, generally somewhat constricted (Fig. 

 247, B), is inserted into the Malpighian capsule, most usually on the 

 opposite side to the afferent and efferent vessels ; but in accordance with 

 what has been said, its cavity penetrates into the capsule, only to an 

 inconsiderable extent ; inasmuch as the latter is almost entirely occupied 

 by the vessels and the epithelium surrounding them.* 



* [With respect to the question of the cereal termination, or commencement, as it miglit 

 more properly be termed, of the tubuli tirinifcri in the Malpighian capsules, there is an 



