220 



constantly sec in tuberculosis. On the contrar}-, as 

 they become older they get firmer and harder, they 

 shew more or less development of fat cells, and they 

 contain fewer bacilli, until at last in an apparently 

 perfectly recovered bird they will be found to contain 

 none at all. 



Extravasations of blood are peculiarly liable to 

 take place in the brain and its coverings and into the 

 hollow spaces between the outer and inner tables 

 of the skull. Indeed it is this apoplexy which is the 

 most frequent immediate cause of death in avian 

 septicaemia. Its production is due to a combination 

 of causes. First there is a detachment of a portion 

 of one of the septic plugs which we have noticed as 

 occurring here and there in the abdominal or general 

 circulation. This fragment being carried on in the 

 blood stream finally becomes impacted in the lessening 

 calibre of a cerebral vessel. Then as a result of this 

 a small aneurism (or dilatation of the arter}^) forms 

 immediately behind the plug, the wall of the vessel 

 becomes rapidly thinned, and finally a rupture takes 

 place with formidable haemorrhage into the surround- 

 ing structures, causing a speedy death by pressure 

 npon the nerve centres which govern and stimulate 

 the physiological actions which constitute life. Or 

 again, the brain haemorrhages may occur from merel}'' 

 the altered blood state to which I have previously 

 alluded. In this case they will be noticed to be 

 generally of small size, but to be multiple, appearing 

 in fact as a number of small dots of varying sizes. 



When, as occasionally happens, a haemorrhage 

 takes place immediately beneath the skin the trans- 

 formation of the clot into a typical nodule takes place 

 in somewhat the same manner as we have seen in 

 other situations, and since this generally occurs in 

 chronic cases the nodule frequently attains to a 

 very large size. In the course of a great number of 



