CHANGES PRODUCED IN LUNG BY OLLULANUS TRICUSPIS. 151 



fatty nature. This is beautifully brought out by perosmic 

 acid. The fully formed encapsuled worm is not blackened, 

 but wherever an embryo is beginning to undergo this change, 

 the perosmic acid blackens the fatty particles, and when the 

 degeneration is complete the capsule appears as if it were 

 filled with a black oval mass. 



With regard to the fully formed embryo, probably the 

 most notable point about it is, that when it is uncoiled it is 

 of comparatively immense proportions, measuring 0*32 mm. 

 in length, whilst the adult female form measures only 

 1 mm. 



Local changes in the blood-vessels. 



Apart from the direct local changes produced by the pre- 

 sence of these parasites, these local changes give rise to 

 other important changes in the blood-vessels of the lungs. 

 By the existence of such a large number of inflammatory 

 lesions, little tubercles, (one may call them) are formed, and 

 encroach upon and obliterate a great number of vascular 

 capillaries and thus destroy a great vascular area, rendering 

 small but excessively numerous foci impervious to the blood. 

 What is the result ? The same amount of blood has to be 

 propelled through the lungs, but now, owing to the presence 

 of these small nodules causing obliteration of many capillaries, 

 the resistance to the passage of the blood through the lungs 

 is increased, and the heart, in order to overcome this resist- 

 ance, must hypertrophy, and the blood-vessels, especially the 

 pulmonary artery, in order to withstand this extra strain or 

 pressure put upon it by the now thickened heart, must 

 either dilate under the tension or become thickened and so 

 strengthened in order to resist this strain. So we find that 

 the pulmonary artery and its branches throughout the lungs 

 has its middle coat greatly thickened. We have here in the 

 case of the lungs the same condition which is found in other 

 organs, e.g., the kidneys undergoing interstitial inflammation, 

 as in a certain form of Brights' disease, leading to thickening 

 of the middle coat of the arteries. Similar conditions obtain 

 in the case of aortic obstruction, which leads to dilatation of 

 the left ventricle and thickening of its walls. 



Fig. \) d, shows a transverse section of the pulmonary 

 artery so thickened, and the lumen has also become 

 diminished. The same is shown in fig. 5, which represents 

 an artery opened into somewhat obliquely, and gives a trans- 

 verse and longitudinal section of the vessel with its immensely 

 thickened middle coat and its diminished calibre. The 

 thickening of the middle coat was extremely well marked in 

 all the arteries of the lungs. 



