644 OCCURRENCE AND MEDICAL IMPORTANCE. 



than thirty years respectively. The reports of Neisser, based upon 

 fifty-four cases, only differ in that comparatively the greatest number 

 of fatal cases occurred within the first two years (that is to say, from 

 the discovery of the parasite, and without taking into account the 

 time during which it had escaped observation). 



The time which the Echinococcus disease takes to reach its termi- 

 nation depends upon various circumstances. Besides the greater or 

 less rapidity with which the parasite grows, it is mainly determined 

 by the physiological nature of the infected structure. But even in 

 the same organ the Echinococcus gives rise to a different prognosis 

 according to its situation ; thus, for example, it is by no means in- 

 different to the host whether a bladder- worm in the liver has developed 

 in the neighbourhood of the great vessels, or among the yielding 

 ventral coverings. Nor is the form of the parasite of little moment in 

 this connection, as is evident from the constancy with which the 

 multilocular Echinococcus leads to the death of the patient through 

 the ulceration of the intermediate tissue. 



So long as the Echinococcus is but of small size, the disturbances 

 which it causes are trifling, unless it occur in a nerve centre, or, as is 

 very rarely the case, in the eye. But as the parasite increases in 

 volume, the seriousness of the disturbance increases. In itself pain- 

 less, it gradually produces a feeling of pressure and heaviness, which 

 continually augments. The affected organ becomes enlarged, and loses 

 its previous form and character. The surrounding body wall is raised 

 up, if it can yield to pressure, and the adjacent organs are displaced. 

 At the same time there sets in a series of functional disturbances, 

 which become more and more aggravated, and which, at first associated 

 with the increasing intruder, not unfrequently spread to adjacent 

 parts. The health of the victim becomes more and more completely 

 undermined ; nutrition suffers, circulation is disturbed, a condition of 

 marasmus results, and finally death supervenes with symptoms of 

 exhaustion, unless a previous dropsical or inflammatory attack bring 

 it about sooner. 



The special symptoms of the Echinococcus disease vary, of course, 

 greatly according to the situation and size of the parasite. A parasite 

 occurring in the liver produces different pathological results from 

 those caused by one occurring in the kidneys or lungs. Even in the 

 same organ the results are very various. The different modifications, 

 as detailed by Davaine and Neisser, and discussed by Kuchenmeister, 

 cannot here be entered into fully ; we must restrict ourselves to a few 

 observations of more general interest. 



In the first place it may be mentioned that the life-history of 

 Echinococcus exhibits hardly any factors fitted to produce a direct and 



