Although, as is well known, the ultra-microscopic viruses are invisible in histological preparations, yet characteristic bodies occur within certain of the cells of animals infected with such organisms. The origin and nature of these so-called “virus bodies” has been the subject of much controversy. By some they have been regarded as the actual parasite, or at least as phases in its life cycle. To von Prowazek they were dual in character consisting of microorganisms embedded in material produced by the reaction of the cytoplasm of the infected cell. Still other observers regarded such bodies as products of cellular disintegration. In a former paper (Findlay and Ludford (1926)) we have referred to the various views held by writers in this field and have made a survey of the literature of the subject in the form of a pictographic review. We shall, therefore, only mention previous work in this field, in so far as it directly concerns our personal observations. A conspicuous fault of much of the earlier work has been the unsatisfactory histological technique employed, especially the nature of the fixative. The earlier cytological work was carried out with fixatives, which although satisfactory for the subsequent demonstration of nuclear structures were very destructive to the cytoplasm. This is particularly unfortunate since most of the virus bodies occur in the ground cytoplasm of cells. We have endeavoured to rectify this source of error in our work by employing fixatives, which have been proved to fix the cells in such a manner as to give an appearance as nearly as possible identical with their structure, as seen in the living cells.
Cytological studies on the viruses of fowl-pox and vaccinia
