94 C. F. MAESHALL. 



Snail, &c, which have to perform much more rapid and regular 

 contractions than the " hearts " of the worm that we find 

 striped muscle developed. 



I may here state that I have not yet been able to determine 

 the nature of the connection between the network of striped 

 muscle and the nerve end-plate, which must exist if the com- 

 bined results of Retzius and Bremer are correct. This I 

 hope to do in a subsequent paper. I have, however, recently 

 observed the connection between the network and the muscle- 

 corpuscles described by Retzius. 



Theory of Muscular Contraction. 



The general conclusions arrived at in the preceding part of 

 the paper are as follows : 



(1) An intracellular network of a definite character is 

 present in the fibre of striped muscle throughout the animal 

 kingdom. 



(2) This network is developed where rapid and frequent 

 movements have to be performed. 



(3) The striped muscle-fibre consists of sarcolemma, network, 

 and sarcous substance ; and, so far as at present determined, 

 there is no other structure present in the fibre (excepting the 

 muscle-corpuscles and nerve-endings). 



The question now before us is to determine if possible the 

 nature and function of the network, and what relation it bears 

 to the contractility of the muscle-fibre. 



Changes in the Network during contraction. — In 

 order to investigate this point I teased out some perfectly fresh 

 muscle from the leg of a Dytiscus and placed it on an inverted 

 cover-glass over a gas- chamber. Alcohol vapour was then 

 blown over the preparation when most of the fibres contracted 

 owing to the chemical stimulus. The vapour was passed over 

 the muscle for about a quarter or half a minute. The fibres 

 were then fixed in their contracted state by plunging them into 

 5 per cent, acetic acid for half a minute, and then treated with 



