18(i 



It is our intention to show that histological diagnosis is both possible 

 and practical. 



Both the pathological anatomical collections of the Grovernment 

 Veterinary Bacteriological Laboratory, and material collected during the 

 investigation of an extremely virulent pleuro-pneumonia virus, offered 

 special facihties for the study of the histology of the lesions of the disease, 

 and the more recent cases have given us a specially valuable statistical 

 material. Unless otherwise stated, the material, on which this paper is 

 based, has been treated with Kayserhng, or with Orth's licj^uid (Formol- 

 Mueller), passed through alcohol to xylol to paraffin. And it may be 

 stated here that Orth's method gives splendid results ; provided that 

 the tissues have been sufficiently washed out they take all the most recent 

 stains and give perfect illustrative preparations. 



The study of the lesions is best carried out proceeding from the 

 already known to the new, and drawing one's conclusions from recognised 

 data of the lungs to compare the other phenomena connected with pleuro- 

 pneumonia. Unless otherwise stated, corrections will only be necessary 

 with regard to microscopical details. 



In a paper " On Microscopically Visible Filterable Vira," Lipschutz 

 deplores without reason the absence of histological records in pleuro- 

 pneumonia, and expresses the wish that investigations should be made with 

 the object to demonstrate the presence of " Einschlusse " (inclusions in cells), 

 or of specific products of degeneration in epithelial cells. I have paid 

 special attention to this question as far as possible on hardened material. 

 I intend to return to this problem elsewhere. 



My object in this paper is not to study the alterations in the cells 

 themselves, but the changes in the histological complexes. First taking 

 the microscopical lesions I will then go over to the microscopical details. 



Macroscopical Lesions in the Lungs. 



All the lobes of the lungs examined were preserved in Kayserling 3, 

 and consequently gave very clear insight into the structure of the morbid 

 changes. It would carry us too far should I analyse in detail each of 

 the pieces at my disposal, especially as we are dealing with well-known 

 data. The general lesions that can be described from about ten lungs 

 and from a similar number of pieces, most of which are taken from 

 chronic cases, or such with high fever, are as follows : — 



The pleura has in most cases undergone the different known changes. 

 The fibrinous, plaque-like, thick deposits on the pleura puhnonalis of the 

 anterior and middle lobe are most conspicuous ; their fibrous consistence 

 points to fibrine. They are easily ruptured, frequently white in the 

 middle, with filamentous surroundings, outlined with dark yellow, some- 

 times, however, only straw-coloured irregular contours, which are fre- 

 quently haemorrhagic infiltrated. 



