D wight.] 120 [Nov. 5, 



repeatedly done, but also because most of the methods employed 

 have been so unsatisfactory as to throw doubt on the conclusions. 



Fibres have been used after removal from the body, teased out by 

 needles, or flattened by the covering glass, and further affected by 

 the abnormal media (among which even air is to be reckoned) in 

 which they were examined. The contractions occurring under these 

 circumstances are irregular, and mostly short-lived. Another very 

 important objection appears to have escaped attention, namely : that 

 when a muscular fibre is removed from the body it has lost its at- 

 tachments, and owing to its properties of tonicity and elasticity it 

 must, either at rest or in action, be in different relations from those 

 of the living fibre, MerkeF states frankly that he never has been 

 able to follow the steps of contraction. He could see the fibre begin 

 to move, the movement become quicker, and then the contraction 

 would be complete without his having been able to see the inter- 

 mediate phenomena. He contrived to obtain permanent views of 

 more or less contracted fibres by throwing small parts of living ani- 

 mals into absolute alcohol, which struck the fibres dead in all the 

 stages of vital action, but he lias disregarded the chances of error 

 from the specific action of the reagent on the substance of the fibres, 

 and on their last movements. Wagener and Engelmann appear to 

 have made some observations on living animals, or on parts of them, 

 but I have seen no detailed account of these studies, and cannot 

 think that they carried them far, for had they done so they certainly 

 would not have relinquished them. 



After studying fibres pulled from the legs of flies and grasshoppers, 

 I turned my attention to water beetles, and accidentally discovered 

 that the legs of several of the smaller kinds were sufficiently trans- 

 parent to give a good view of the muscles in situ, but that the genus 

 Gyrinus is far superior to any other. The method is very simple: 

 a leg of either the middle or hind pair is cut off, between the coxa 

 and trochanter if possible, and put on a slide in a drop of water un- 

 der a very thin covering glass. Care should be taken to have the 

 leg tolerably straight, for if much flexed some of the best parts are 

 obscured. The muscles are here in an almost perfectly normal con- 

 dition, for their attachments are uninjured, and the water in which 

 the leg is placed (its native element, by the way) can hardly pene- 

 trate beyond the joint below the point of division. The only disad- 

 vantage is that the specimen is cut off from its nutrient and nervous 

 supplies. A successful experiment affords one of the most striking 



1 Archiv fur Mikroskopische Anatomie, Band vrn, Heft 2. 



