1873.] 125 [Dwight. 



observers are not in harmony, and it may well be questioned whether 

 results obtained by its use on fibres hardened by reagents, are of any 

 particular value. In the case of the entire leg, it proved unavailable, 

 for the presence of two layers of shell, enclosing often more than one 

 layer of muscle, rendered the few results which I obtained quite un- 

 trustworthy. It has been stated that the staining qualities of hgema- 

 toxylin make it a substitute for polarized light; accordingly I repeat- 

 edly put a living beetle into a pretty strong solution; but though I 

 once left one in for twenty -four hours, during the greater part of 

 which time life was extinct, the tissues showed that none of the col- 

 oring matter had passed the skin, so that I was obliged unwillingly to 

 give up this class of experiments. 



By the kindness of Professor Henry P. Bowditch, I was enabled 

 to perforin in his laboratory a series of electrical experiments with 

 both the constant and the interrupted current. The effect of a sin- 

 gle shock, or of the use for a short time (say a minute) of a weak 

 interrupted current, was to produce lively, though irregular action ; 

 the waves ran in both directions simultaneously. If a strong inter- 

 rupted current were used, or a weak one were long continued, the 

 muscle became tetanized; the waves of contraction ceased, and 

 whole fibres assumed the appearances of the extremest contraction 

 throughout ; nothing could be seen but a succession of very narrow 

 black and white lines. The experiments with the constant current 

 promised to be of great interest, but as they were very difficult, and 

 threatened to lead me far beyond my original plan, I soon decided to 

 leave them for abler hands. 



Let us now glance at the difference of the results obtained by this 

 method, and by examining fibres taken from the legs of the large 

 water beetles, Hydrophilus and Dytiscus. For the appearances of 

 those of the Hydrophilus, I have used Heppner's plates Qoc. cit.), 

 and for those of the Dytiscus, original observations on fibres from the 

 leg without any reagent. The muscles of the two are precisely simi- 

 lar. By comparison with those of the little Gyrinus, in situ, it ap- 

 peared that the fibres of the larger beetles were much broader, but 

 that the stripes were in proportion much nearer together. To see if 

 this did not depend on the abnormal condition of the larger fibres, I 

 endeavored to obtain fibres from the Gyrinus. There was little diffi- 

 culty in doing this if a leg, or a part of the abdomen, were broken to 

 pieces in a drop of fluid, but unfortunately it was almost impossible 

 to separate the muscles from the shell without such addition, and 



