KLEIN ON THE PATHOLOGY OF SHEEP-POX, 229 
striking instance of design, or as some would have it, adap- 
tive direction of force, does not exist, in an organ so abound- 
Ing in wonders as the eye. 
On the PatHotoay of SueEep-pox.! By Dr. Kiet, F.R.S., 
Assistant Professor in the Brown Institution Laboratory. 
VARIOLA OVINA, or sheep-pox, is a disease which, although 
it is not communicable to man, and possesses a specific con- 
tagium of its own, very closely resembles human small- 
pox, both as regards the development of the morbid process 
and the anatomical lesions which accompany it. ‘This 
correspondence is so complete that it cannot be doubted that 
the pathogeny of the two diseases is the same. That is to 
say, that whatever explanation can be given of the way in 
which the material cause or contagium produces its effects in 
the one case will also serve as a key to the understanding of 
the other. The present investigation was therefore under- 
taken in the confidence that the application of the experi- 
mental method to the investigation of the ovine disease 
would not only yield results of value, as contributory to our 
knowledge of the infective process in general, but would 
throw special light on the pathology of smallpox. 
In the following pages I propose, after giving an account 
of the method of investigation employed, to describe, first, 
the microscopical character of the sheep-pox virus, and 
to compare them with those of vaccine lymph. I shall 
then proceed to detail the results of my investigation of 
the pathological changes which occur in the affected parts 
of the skin. 
Section I.—Method of Investigation. 
The purpose of the inquiry being to determine the nature 
of the pathological process, of which the cutaneous eruption 
is the most prominent, and probably the most important 
manifestation, it was necessary to examine the affected skin 
anatomically in all stages of the development of the disease. 
In order to obtain the material for this investigation, I com- 
municated the disease by inoculation to a sufficient number 
of sheep. In this way I obtained specimens of skin, corre- 
1 Reprinted from the ‘ Reports of the Medical Officer of the Privy Council 
and Local Government Board,’ New Series, No. 3, by permission of the 
Lord President of the Council and of H.M. Stationery Office. 
