Journal of Applied Microscopy 



and 



Laboratory Methods 



Volume VI. JULY, 1903. Number 7 



On the Use of Compression in the Study of Small 



Organisms. 



This article is intended to give an account oi methods which have proved 

 useful in the study of small soft animals such as Hydra and certain flukes, and 

 is offered to the readers of this Journal, not as an original contribution to ana- 

 tomical technique, but to call these methods to the attention of any who may 

 not know about them or may not have been making as much use of them as they 

 deserve. It may be supposed that the reader has a working acquaintance with 

 the methods employed in studying whole specimens, either alive or after technical 

 treatment. 



To take the case of living Hydra first : a large gathering of Hydras is made 

 and the well expanded specimens are looked over carefully with the aid of a 

 large reading glass, so that those showing the organization most completely, as 

 to buds, gonads, etc., as well as size, may be used. The specimen is removed 

 with a pipette to the center of the stage of a compressor. I have found the 

 instrument sold by Bausch &: Lomb, the one designated as " life box with spiral 

 slot," the most convenient instrument for this purpose ; the cover is capable of 

 being screwed down, its motion governable by the slot, and different degrees of 

 compression obtained as desired. By observing the animal under the micro- 

 scope during this action, the amount of compression needed to demonstrate the 

 organs, and the degree which the organism can sustain without damage is 

 regulated. 



Frequently long continued observation is needed before many desired details 

 of the structure, especially in a complex organism, come out into view. 1 have 

 noticed this repeatedly in studying the trematodes. Thus, in studying Cotylaspis 

 a form common in Anodonta, it was only after several hours' compression and 

 continuous observation that I found it possible to recognize the details in the 

 structure of the excretory system, details which cannot be ascertained at all in 

 any other way, as they do not show in preserved specimens however they may 

 be treated. Looss, the great student of the trematodes, recommends enclosing 

 trematodes under a cover-glass in water in a ring of an oil, hardening at ordi- 

 nary temperatures, to prevent the evaporation of the water, so that the worm can 

 be kept for several days, and he says that he made most of the observations 



(23',t7) 



