PATHOLOGICAL EFFECTS OF PRESSURE. 



129 



pressure of the foreign bodies which they contain, a more or less con- 

 siderable hypertrophy in the surrounding tissue, and ultimately be- 



FIG. 76. Kidney of Nasua socialis, with 

 Ewtrongylus in the distended pelvis. 



FIG. 77. Muscle- Trichlrtce, seven weeks 

 old, in the distended sarcolemma- 

 sheaths. 



come so much altered, that haemorrhage ensues, and they discharge 

 their contents into the urinary passages. Similarly an active multi- 

 plication of cells has been observed to take place within the space where 

 ova have been deposited by the Strongylidse of the lung, 1 and round 

 about the so-called " Psorospermiae " (Coccidium, Leuckart), which have 

 wandered into the epithelium. But the cells which are inhabited by 

 the Psorospermise themselves are destroyed by the growth of the latter. 



Such changes have, of course, an effect upon the functions of 

 the infected organs. More or less serious disturbances arise, which 

 affect the general health in various ways, according to their inten- 

 sity, and the physiological importance of the invaded organ. 



The parasitism of Distomum Ticematobium is followed by haema- 

 turia, and parasites in the brain give rise to imbecility, paralysis, 

 madness, or convulsions, according to their situation. 2 Similarly, the 



1 Bellinger, " Zur Kenntniss der desquamativen und kasigen Pneumonic," Archiv fur 

 exper. Pathologic u. Pharm., Bd. i., 1873. 



2 A very familiar example of this is afforded by sheep suffering from the disease called 

 " staggers," caused by Coenurus in the brain. (See Numan, " Over den Veelkop-Blaas- 

 vorm der Hersenen," Verhandl. koninTd. Nederl. Inst. Wetensch. [3], Bd. iii., p. 225, 

 ] 850). The pressure exerted by the Coenurus is often so great that, if the worm be in 

 a peripheral position, even the bones become absorbed, and the neighbouring parts of the, 

 skull become quite flexible. 



I 



