PROLIFERATION OF ECHINOCOCCUS MULTILOCULARIS. 627 



fill them, usually varies in such a manner that the largest cavities, 

 which sometimes have a diameter of 3 or 4 mm., are found in the 

 middle of the swelling. But between them are much smaller bladders, 

 and towards the periphery these gradually become more abundant, 

 bladders of less than O'l mm. being not unfrequently found. 



All the bladders, even the smallest, exhibit the well-known 

 structure of the ^c/imococcws-bladder. They possess a laminated, 

 transparent cuticle of great elasticity and considerable thickness, 

 which, in the larger bladders, measures 0'08 mm. or even more, but in 

 the smaller ones sometimes only O01 mm. Occasionally one finds 

 bladders, even among the larger ones, with still thinner walls, so that 

 here, too, the same variations are observed which we noticed in the 

 newly developed SJchinococci. As in the latter, the interior of the 

 bladders is at first filled with a molecular mass, whose coarser granules 

 exhibit a distinctly fatty lustre. As soon as the bladder grows the 

 central space becomes clear, and the former granular contents appear 

 in the form of a membranous lining of the cuticle, with more or less 

 large and abundant calcareous corpuscles. In the parenchymal layer 

 of the larger bladders, Virchow very "frequently observed a large- 

 meshed network of anastomosing, stellate structures, somewhat swollen 

 at the nodes, and extremely fine in the connecting threads, which, being 

 embedded in the hyaline, structureless, intervening substance, pre- 

 sented the greatest resemblance to the stellate cells of the gelatinous 

 tissue. In some places the cells were larger, their processes and 

 connective threads broader and canal-like, their bodies larger (some 

 even 0*2 mm. long and O'l mm. broad), and with a more distinct 

 granular deposit. They had thus a very striking resemblance to 

 lymphatics in the course of development." There can be no doubt 

 that the structure thus described by Virchow, and afterwards in a 

 similar manner by Friedreich, is identical with that which I observed 

 in the large, still headless JEchinococcus-\Asid.dQTS. 



But in the great majority of the bladders of this Echinococcus the 

 heads are never developed. In the foregoing cases I examined many, 

 both large and small, before finding a head, and such has been the 

 experience of earlier and more recent investigators, while many have 

 sought them quite in vain. In my observations the bladders which 

 contained the heads were usually of medium size perhaps 2 mm. or 

 more but the heads were always either isolated or in groups of three 

 or four. In size and form the hooks (36-42 in number) exhibited no 

 differences from those of the usual human JEchinococci. 



Under some circumstances, however, the multilocular Echinococcus 

 attains a considerable fertility. So was it at least in a case from the 

 Zurich Hospital investigated by Marie Prougeansky, in which half 



