ECHINOCOCCUS ALTKICIPAKIENS. 227 



mission of undulations of concussion, the fluid must be the better 

 adapted for the production of this phenomenon when it has a 

 certain degree of viscidity, but not so high as to impede the 

 tremulous motion of the walls of the vesicles themselves; and, 

 lastly, a particular position of the daughter-vesicles at the moment 

 of trembling. With regard to the latter, we should certainly 

 take into consideration the circumstance whether one or more of 

 the daughter-vesicles are attached to the mother-vesicle, which is 

 shaken by percussion, or swim freely in the fluid ; and perhaps 

 even the circumstance whether or no such daughter-vesicles are 

 attached to the spot agitated by the percussion. 



6. For this very reason we have also indicated that the 

 phenomenon of the hydatid-trembling will neither occur in all 

 cases of E. altricipariens, nor uniformly at all times in the same 

 case ; that it may sometimes occur and sometimes be absent in 

 one and the same case, but that, where it occurs, it is one of the 

 most important symptoms, and often alone raises the diagnosis to 

 one of probability. 



7. For the less experienced even this symptom will not be 

 absolutely infallible, as it requires practice to distinguish it from 

 the sensation of fluctuation or trembling occurring in gelatinous 

 pneumonia or in tumours. 



8. Acephalocysts being only barren Echinococci, as we shall 

 show in the following Appendix, what we have said of the 

 two species of Echinococcus applies equally to them ; but in 

 other respects an acephalocyst is not of particular importance 

 to us. 



In reference to all other symptoms, such as the objective 

 symptoms of compression of the organs caused by the size of 

 the swelling, swelling of the extremities by pressure, &c., and the 

 subjective symptoms produced by the swelling, the reader may 

 consult the text-books of special pathology, therapeutics, and 

 surgery. 



As to the etiology of this disorder, no one now-a-days will 

 believe in its production by a blow or fall upon the organ where 

 the Echinococcus is situated, or in any conjectures of that kind. 

 As the only cause, remains the swallowing by the patient, at 

 some period of his life, of one or more eggs or six-hooked em- 

 bryos of the Taenia Echinococcus allricipariens. Neither is it 

 allowable to refer to telluric influences; but, nevertheless, we 

 must remember that the mode of life of men in particular locali- 



