and Laboratory Methods. 1545 



in malignancy by eitlier cancer or tuberculosis. This is the more surprising in 

 that the cestodes are as a rule, though dangerous, still far from malignant. But 

 for many years the differences between the many small chambers of the alveolar 

 type and the great hydatids were set down as the effects of individual variation, 

 and the Taenia echinococcus v. Siebold was held responsible for both species of 

 reaction. 



It is of course somewhat out of fashion in these days to work upon parasites 

 without recourse to experiment. Fresh material was, however, not accessible to 

 Malnikow-Raswedenkow. And by histological study alone, several capital points 

 have been brought out. No intermediate host appears to be required (a char- 

 acter resembling the trematode rather than the usual cestode type of attack). 

 The embryo, doubtless of intestinal origin, makes its way by the blood stream 

 to its favorite site in some small vein just beneath Glisson's capsule. Here a 

 multilocular chitinous structure is formed, wholly analagous with the mature 

 segment (proglottis) of the tape-worm. The chitinous walls are lined not only 

 within, as in the great single hydatids, but also externally with a layer of 

 granular protoplasm in which are produced not only scoleces, as in the hydatid, 

 but also young parasite forms, without capsule, and ovoid embryos, with capsule. 



By release from the outer wall of the cyst, metastasis in this form is rendered 

 much easier than in the unilocular type. The discharged embryos, in case they 

 do not forthwith succumb to phagocytosis within the tissue spaces, gain entrance 

 to some blood vessel, or perhaps a bronchiole, and there form more chitinous 

 cysts. As a consequence of their more intimate contact with the body fluids, 

 the new cysts lose in virulence and usually remain sterile. It is probable, more- 

 over, that feeding experiments may fail for similar reasons if the material is 

 metastatic. 



The affection works by no means simply through pressure or mere mechanical 

 destruction, but toxically as well. Proliferation, phagocytosis, and local tissue- 

 necrosis occur, and in places true granulomata are formed, characterized by the 

 presence of lymphoid cells, epithelioid cells, and giant cells, with caseous 

 degeneration. 



The technique employed is in brief as follows : 



1. Fix in 4 per cent, formaldehyde, 24 hours. 



2. Harden in alcohols of increasing strength, cut from celloidin. 



3. Place from water into Weigert's elastic tissue stain, 3(J minutes. 



4. Wash, decolorize in 90 per cent, alcohol 2 minutes, dip in weak 



lithium carbonate solution, and wash. 



5. Stain with alum-haematoxylin and either eosin or Van Gieson's mixture. 

 The histological appearances are adequately shown in colored plates, of 



which a good example is Taf. iii, Fig. 25, showing penetration of the elastica by 

 young forms of the parasite in the act of invading an hepatic vessel. 



E. E. Southard. 



