153 



the subcutaneous tissue are separated by minutely granulated masses, 

 except in such places or around hair follicles. The cells are rich in proto- 

 plasm and enlarged. On sections through pieces of the tail the changes 

 in the muscles and in the fat are most prominent. As I intend to deal 

 with the muscles at greater length further on, I will now only make a 

 few remarks about the lesions in the adipose tissue. The margins of the 

 globular tissue consist of dense tissue filled with elastic fibres and very 

 many nuclei. In some sections the masses of leucocyts have the appear- 

 ance of a demarcating line, in other places they seem to originate from a 

 recent invasion. In the first case one finds fragments of nuclei and 

 fibrino, in the second case irregular tangled capillaries surrounded at 

 a distance of 20 ,« to 60 ^ by a ring of fibrine. Where the fat approaches 

 the fascia a layer containing a great number of nuclei separates the two 

 tissues, and the fascia itself is weakened by friable masses. It must, 

 however, be pointed out, that ischaemic necrosis is only found at the base 

 of the tail, a distinct lymphangitis is usual nearer the apex. 



In accordance with the anatomical structure is the reticulation of the 

 papillary stratum ; all processes of infection are passed through in this 

 layer of the skin. Later on one finds crowds of leucocytes around the 

 hair follicles. The necrotic parts are separated by the usual demarcatory 

 processes ; in their immediate surroundings the capillary vessels are 

 thrombotised, . and frequently even in resorption. Such places are not 

 frequently found unmixed, usually there are regeneratory foci forming 

 neoplastic connective tissue. Quite close to them, young spindle-shaped 

 cells are forcing themselves between the leucocytes and deposits of exudate 

 which in later stages replace the described lesions by prohferation. In 

 such a condition it is difficult to say histologically what irritation has been 

 caused by the layers of connective tissue between and around the muscles. 

 The condensation of the nucleated tissue around the blood vessels in the 

 subcutaneous strata may perhaps show that an inflammatory process has 

 existed around the vessels. 



It is interesting to demonstrate that whichever tissue may have been 

 the seat of injection of pleuro-pneumonia virus it always shows exactly 

 the same changes as have been described as being found in the interstities 

 of the lungs under natural infection. Practical experience shows that 

 after a period of incubation of twelve to fifteen days, the swelhng creeps 

 along the course of the lymph vessels centripetally, starting from the point 

 of injection, and cause the usual complications, such as necrosis of the 

 apex of the tail, peritonitis, etc. 



It has been stated that contamination of the vaccine is the cause of 

 comphcations. I quite disagree with such a notion, for, working with 

 absolute pure cultures and taking all aseptic precautions, we yet cannot 

 avoid having losses. Individual disposition, or weakening of the con- 

 stitution, form the cause of the misfortune. 



