1. The contagious venereal tumour of dogs has been examined for the
first time by modern cytological technical methods and the cytoplasmic
2. Adequate technique, controlled by observations on the living cells,
shows that these tumour cells are exceedingly rich in lipide globules, the
presence of which has been overlooked (a) because they are dissolved out from
paraffin sections and (b) because in frozen sections they are refractory to the
customary methods for the demonstration of fatty substances. To stain these
globules, the use of a specially devised acetic-carbol-sudan method is
3. Previously employed methods of studying the tumour cells have been
misleading - as indeed they were doomed to be - not merely because of failure
to demonstrate the lipides, but still more because of the extensive artefacts
which result from failure to take precautions against shrinkage of the cells
which follows dissolution of this constituent, which occupies so large a
part of the cytoplasm. Current views - that the contagious venereal tumour
is composed of round cells or of stellate cells (reticulum cells) - depend
entirely on the examination of material showing such fixation or rather
4. The cell membrane is highly developed and the cells are polygonal in
shape and closely aggregated together as in an epithelium.
5. The granules (mitochondria?) are distributed throughout the cytoplasm
and are less constantly stained by the classical mitochondrial
techniques than are the mitochondria of most other cells. Technique suitable
for their demonstration is described.
6. The Golgi apparatus is well developed and has the form of a spiked
wreath, one-third to one-half the size of the nucleus.
7. The centrosome and the achromatic spindle have been demonstrated
and described. Measurements of the spindle angle reveal a mean value of
114°, contrasting with the angle of cells of the lymphoid series as measured
8. Routine diagnosis of the contagious venereal tumour is more rapidly
and certainly accomplished by means of teased preparations than by the usual
sections. Pitfalls in the differential histopathological diagnosis have been
explained, especially from mastocytoma and endothelioma.
9. According to present conceptions of the structure and habitus of
large lymphocytes (lymphoblasts) it would be difficult to identify the tumour
cells with these elements.
10. Accordingly, further support is provided for the author's alternative
theory that the contagious venereal tumour may be an apolar neuroblastoma.