1 64 THOMPSON YATES LABORATORIES REPORT 
layer, and a lining of epithelioid cells within, polyhedral or even cubical. Apart from 
the capillaries which are present in the developed glomerulus, the glomerular tuft is'i 
formed by a local proliferation of these epithelioid cells, and of the membrana propria 
or limiting layer, these both covering and passing in all directions between- the 
capillary recticulum. The epithelioid cells become squamous in the adult state. 
This structure is identical with a definite stage in the changes of the pseudo- 
cystic bodies. It has been seen that a few young specimens appear as solid masses of 
polyhedral cells, encircled by a limiting layer of flattened cells, and that later the 
central polyhedral cells become squamous. 
The absence of the glomerular capillaries does not negative the identity, as 
they are a secondary in-growth. In their absence no glomerular cavity would develop, 
depending as it does on secretion derived from the capillaries, and instead, the 
squamous cells which normally form a lining and a support tor the internal structure 
of the glomerulus, fill the whole interior of the limiting layer. The pseudo-cysts are 
therefore to be looked upon as Malpighian corpuscles. The structure is sufficient to 
decide the identity, and it is supported by the presence of the tubules which lie 
adjacent to and around the pseudo-cysts. Whether these tubules are in this position 
or more isolated, they must be considered the representatives of the primitive tubules 
from which the uriniferous tubules develop. 
The new growth is therefore traceable to a perversion of the cellular elements 
from which, under normal development, Malpighian corpuscles and uriniferous tubules 
arise. The result of this perversion is the production of a tissue largely consisting of 
fat cells, but also in varying proportion of round cells, with large nuclei in a scanty 
stroma ; in addition young striated muscle cells and young connective tissue cells are 
unequally distributed throughout the structure. A name cannot be given to such a 
tumour on the general principle that malignant tumours arising from glandular 
epithelium are carcinomata, and those arising from connective tissue are sarcomata. 
The principle would seem to apply to growths originating from a substratum of adult 
cells, but in such a case as the present its application presents, among others, the 
following difficulties. The cells in many situations have obviously arisen as a 
proliferation of those of the tubular epithelium, on the other hand the resulting growth 
is composed of solid masses of round and irregularly shaped cells, and the structure 
is what is commonly called sarcomatous. 
Birch-Hirschfeld* in describing a somewhat similar tumour remarks that 
these primary malignant growths of the kidney belong to no one group in the present 
classification, and gives to that under his consideration the name ' sarcomatous glan- 
dular tumour or the kidney.' Other authors have remarked on the same difficulty 
in nomenclature, and until the growths which apparently arise in connection with 
irregularities in embryological processes can be separately classified, it will be im- 
possible to arrive at any satisfactory solution. 
* Birch-Hirschfeld. Ziegler's Beit/. Z. Path. Anatom. Bd. xxiv. P. 343. 
