1885.] 



Taenia Echinococcus in the Dog. 



449 



additional circulation, there are three, together with a standing wave 

 (corresponding to an infinite period). When both additional circula- 

 tions are present the periods are given by a biquadratic equation. 



When there is no rotational core the motion is always stable. When 

 there is a doubly continuous core whose density is greater than that of 

 the surrounding fluid there must in general be an additional outer 

 circulation to render the ring stable. After a hollow is formed the 

 simple ring usually treated of is still stable. But if the core is denser 

 than the surrounding fluid, it is always stable only if the outer addi- 

 tional circulation is larger than a certain critical value, depending on 

 the densities and the circulations. If it is less than this critical value, 

 the ring becomes unstable at some point as the aperture increases. 



XII. " Notes upon the Experimental Breeding of Tcenia Echino- 

 coccus in the Dog from the Echinococci of Man.'* By John 

 Daytes Thclmas, M.D. (Loud.), F.R.C.S. (Eng.), lately 

 Physician to the Adelaide Hospital, and Member of the 

 Council of the University of Adelaide. Communicated by 

 T. S. Cobbold, M.D., F.R.S. Received June 8, 1885. 



The cystic parasite, Echinococcus, is known to occur' under four 

 forms, viz., as — 



1. The Acephalo cystic form. 



2. Echinococcus scolicipariens. 



3. „ altricipariens. 



4. „ multilocularis. 



As regards the Acephalocystic form first described in 1804 by 

 Laennec, it is now generally regarded as a sterile variety in which 

 either no brood-capsules and scolices have been formed, or in which 

 such structures have once been present, but have degenerated and 

 disappeared. 



Echinococcus multilocularis is believed to owe its peculiar characters 

 to the fact that it has developed, within tubular structures, e.g., the 

 lymphatic canals (Virchow), the blood-vessels (Leuckart), or the 

 biliary canals (Schroder van der Kolk, Friedreich, and Morin). 



It is not probable that this unusual growth is connected in any wav 

 with the biliary canals, because it has been found not only in the 

 liver but also in the lungs and peritoneum. 



Echinococcus scolicipariens and Echinococcus veterinorum were long 

 regarded as distinct species. Their distinctive characters being — 



(a.) A marked difference in the mode of proliferation. In Echi- 

 nococcus scolicipariens brood-capsules and scolices being produced, 



