32 JOURNAL OF THE [January, 



the preserving liquid. But, on account of the irritation to which 

 the animal is subjected by this method, abnormal contractions 

 usually occur. It is consequently advisable to first paralyze the- 

 muscular system with hydroxylamine, then to flatten the animal 

 under the cover g!ass, and finally kill it with picric-acetic acid. 

 For paralyzing Dendrocoeluin lacteum ten or fifteen minutes are 

 sufficient, with a 0.5-per-cent solution of hydroxylamine chlo- 

 ride. The moment the animal stops moving is the best time 

 to kill it. 



6. Hirudo medicinalis. — To produce good sections of leeches 

 the body must show no contraction after being killed. Chloro- 

 form as a paralyzing agent cannot be recommended, as, on ac- 

 count of excessive irritation, the muscles of the leech are often 

 torn. When placed in a i-per-cent solution of hydroxylamine 

 chloride, the animals stretch themselves out to their full normal 

 length after from one-half to two hours' time, and remain in this, 

 state after the fixing medium is added, which may be either alco- 

 hol or picric-acetic acid. 



7. Nais proboscidea. — Nais has a tendency, when placed in the 

 preserving fluid, to roll itself up sideways and perceptibly shorten 

 its segments. A side view of the body is of course advantageous 



or the study of the nervous system, but the segmental organs are 

 not visible in this position, as they are covered by the intestines. 

 In order to properly see them the animal must be fixed on its 

 belly or back, when the entire segmental structure is shown. 

 Place the Nais in a o. i-per-cent solution of hydroxylamine 

 chloride. After twenty or thirty minutes the skin muscles are sa 

 lame that the animal hardly moves, and may be fixed on the slide 

 in any position with picric-acetic acid. The specific muscle-par- 

 alyzing action of hydroxylamine is especially noticeable in Nats 

 proboscidea, for the animal may remain one hour and a half in the 

 hydroxylamine solution without the ciliary motion in the rectum 

 entirely ceasing, while the skin muscles have become incapable of 

 contraction after about half an hour. Moreover, Nais is able to 

 recover its natural condition if transferred to pure water. The 

 ciliary motion of the rectum again becomes active, and later the 

 skin muscles regain their contractile ability. It is consequently 

 possible, after thoroughly washing the paralyzed animal for about 

 ten minutes, to kill it with other reagents than picric-acetic acid — 



