194 
On the Structure and Development of 
Henle at an earlier period had described, as cells of this tissae, 
bodies that were like little plates, arranged in rows.* He un- 
doubtedly was one of the first to get a correct conception of the 
real nature of these bodies. Later, Rollett also expressed some- 
what similar views.f 
Subsequently, great advances were made in these studies, at 
first by the use of acetic acid, which rendered the nuclei visible, and 
later, by the discovery of certain reagents which differentiated the 
elements even more strongly, and also by the application of certain 
fluids, such as Miiller's fluid, which separated the bundles into 
their components, the fibrils. 
Eanvier has really had most of the credit for directing the 
attention of histologists to the plate-like corpuscles, though, as we 
have seen, Henle had. already mentioned them, and Eanvier himself 
credits him with their discovery.^ 
Billroth also described them in 1858. Eanvier, however, gave 
the most distinct statement that had been made of the relations 
the corpuscles bore to the fibres. He said that these plate-like 
bodies formed a sort of investing sheath about the bundles, and so 
constituted hollow cylinders, something like drain pipes, the plate- 
like bodies themselves being held together by a firm, cementing 
substance. In some cases, however, these plates were not firmly 
united together in rows, but had considerable spaces between them, 
forming open or incomplete tubes. He stated, in fine, that con- 
nective tissue (by which, however, it is not clear exactly what 
varieties he meant it to include) was formed essentially of bundles 
of fibres, of elastic tissue, and of cells, and the bundles were 
cylindrical. 
There were only two kinds of cells, one kind flat, containing 
granular protoplasm and nuclei, and having irregular outlines and 
prolongations ; the other round and having nuclei, and not to be 
distinguished from white blood-globules. 
Among the comparatively recent studies are those of Loewe. 
This author has thrown a great deal of light upon the subject of 
tendons, especially upon their sheaths, which he believes are lined 
with endothelial cells, and constitute passages for the flow of 
lymph. He states also that the tendon bundles are covered 
with a continuous and closed sheath which is made up of the 
plate-like cells imbedded in an amorphous elastic ground sub- 
stance, and that the bundles present the same characters for great 
distances. 
These corpuscles, " Eanvier's cells," are also covered by another 
layer, which he calls the sub-endothelial layer, and which can be 
* Canstatt's ' Jahresbericht,' 1851, p. 23. 
t Henle and Pfeufer's ' Zeitschr.,' 1859. 
X ' Archives de Phys.,' 1869, ii., p. 471. 
