do4 
rather than development, and is unable to distinguish certain features, 
such as nuclear structure, spore formation, and multiplication, which 
characterize the well-known protozoan parasites. 
Ewing finds the nuclear forms specific to smallpox, but does not con- 
sider that sufficient proof has been adduced to identify them as organisms. 
He finds them identical in staining reaction with nucleoli and linin 
globules and claims to demonstrate transitions between the latter and the 
larger vacuolated forms. The presence of these structures in cells 
advanced in degeneration he regards as against the parasitic theory. 
Howard and Perkins (9) confirm the life cycle of cytoryctes as 
presented by Calkins and present a hitherto undescribed secondary 
cytoplasmic stage. They believe that it is this form which first invades 
the nucleus and gives rise to the nuclear phases previously described. 
Ewing (8) in a more recent publication presents results obtained by 
the application of the Klalsch method of making histological prepara- 
tions. He claims that by this method there is less artefact, especially 
as. regards shrinkage, than in tissue fixed and sectioned by the usual 
methods. After applying this technique to the study of vaccine lesions 
of the cornea and skin he concludes that the vaccine body is a portion of 
the cytoreticulum, the alteration in its staining reaction being due to 
a diffusion of nuclear proteids into the cytoplasm. He suggests the — 
possibility of the presence of specific organisms within these “degenera- 
tions.” He admits the vaccine bodies to be specific to variola and 
vaccinia. 
Siegel (11) confirms previous descriptions of the cytoplasmic forms, 
but suggests that the nuclear forms described by Councilman are post- 
mortem artefacts. He bases this inference on the statement of 'Tyzzer 
that he was unable to find these intranuclear forms in perfectly fresh 
tissue, and utterly disregards the experimental work on monkeys in 
which the presence of the nuclear bodies was shown in perfectly fresh 
tissue, 
Davidson (6) studied the tissues of a case of variola and found the 
cytoplasmic but no nuclear forms. 
Shrumpf (10) does not consider either the nuclear or cytoplasmic 
inclusions to be organisms. His conclusions do not seem to be based 
upon very extensive studies. 
Technique.—Vhe details of inoculation in the series of experiments 
from which our material for this study was obtained are given in full in 
other sections of this paper and need not be repeated. However, atten- 
tion is called to the fact that the method of making multiple inoculations 
upon the skin furnished lesions of sufficient number to excise one at each 
24-hour interval from the time of inoculation until repair had begun. 
By this method it is possible to obtain all stages of the process in each 
animal. In the study of the disease produced in other ways than by 
inoculation upon the skin, animals of a given series were killed at regular 
