and Laboratory Methods. 1581 



them out on glass plates with soft brushes, and fixing them in sublimate solution 

 while held in this position. Other trematodes, large and small alike, are very 

 well prepared as follows : One or two cubic centimeters of the intestinal contents 

 are put in a test-tube one-third full of normal salt solution and shaken vigor- 

 ously for one-half to one minute. Concentrated sublimate solution is then added 

 to the amount of one-half the quantity of salt solution in the test-tube, and the 

 shaking continued for one-half minute longer. The parasites die in an extended 

 condition, and, if need be, may remain four to six weeks in the sublimate solu- 

 tion without injury. 



The worms may be freed from extraneous material by repeated shakings and 

 decantations, and put through alcohol grades and iodine-alcohol. When numer- 

 ous small trematodes are amid the intestinal villi they may be secured by cutting 

 the intestine in small pieces and shaking these vigorously in normal salt solu- 

 tion till the worms are freed, when the intestinal fragments can be removed and 

 the worms treated with sublimate. In many cases the duration of the shaking 

 must be adjusted to the contractility of the parasites present. Large species 

 should be placed in fiat-bottomed dishes till hardened. If possible, a few speci- 

 mens of each species should be killed in TO per cent, alcohol on a slide beneath 

 a cover-glass, supported by wax feet. The alcohol should be changed from time 

 to time, and when the killing is completed the whole should be transferred to 

 90 per cent, alcohol, and freed from the slide and cover-glass. 



Cestodes. — Small species with chains of proglottids, such as Taenia echinococcus, 

 are preserved by the above described shaking method. It is advisable in all 

 cases to test the tenacity of the proglottid chains before submitting them to the 

 shaking process, for some forms readily break up when shaken. In such cases 

 a moderate movement of the preserving fluid suffices to preserve the worms in 

 an extended condition. Larger forms, including many fish and reptile tape- 

 worms, become tangled if shaken. These should be stretched out on glass 

 plates to harden after the first few minutes exposure to the killing fluid. Tape- 

 worms exceeding 5 cm. in length should not be subjected to the shaking process, 

 but may be gathered in shallow dishes in normal salt solution. From this they 

 are taken singly, by grasping the posterior proglottid with forceps, and are 

 shaken to and fro in a one to two per cent, solution of sublimate in normal salt 

 solution until contraction ceases. When the posterior proglottids are too readily 

 detached, the worm should be held near the middle of the chain. Very large 

 worms, such as Taenia saginata and Motiiezia expansa, etc., are not easily shaken 

 out in the ordinary dish of killing fluid. Fine specimens may be secured, how- 

 ever, by pouring the concentrated sublimate solution over the worms, suspended 

 across the palm of the left hand so that the head and the end of the strobila 

 hang free. 



Nematodes. — Small species, such as Strongylus subtilus, when present in con- 

 siderable numbers, may be collected and cleaned by the shaking and decantation 

 method above described, treating, however, but a small amount of the material 

 at one time in the salt solution. Species with thin cuticula (Strongylus from the 

 lungs, Filaria from the body-cavity) should be placed in 1-1.2 per cent, salt 

 solution to avoid the swelling which attends the use of weaker solutions. The 



