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Dr. W. Kuhne. On the 



taking up any other. Tims the movement cannot become more 

 ordered until obstacles confine and direct it. Between the perfected 

 organisation of contractile substance in muscle and that of protoplasm 

 capable only of unordered movement, we meet a succession of signi- 

 ficant steps by means of which we can see how the ordering was 

 attained. The first step would seem to consist in the uncommonly 

 widespread flagellar and ciliary motion, in which an elastic structure, 

 affixed on one side to the contractile mass, is drawn down or bent by its 

 movement, straightening out again in the rhythmic pauses of repose. 

 A further step, at wbich the contraction can only take place along an 

 axis, consists in the arrangement of the protoplasm in fine strips 

 wholly or partially surrounded by elastic walls, or again in elastic 

 fibrils being embedded in protoplasmic processes. In this case we 

 have actual primitive muscles before us, of which the most elegant 

 examples are known in the Infusoria among the Vorticellee and 

 Stentores. The movement of these structures is quite like that of 

 muscle. The strips lengthen and thicken, and they may also be con- 

 tracted in quick twitches or in a prolonged tetanus, the relaxing, 

 like the stage of diminishing energy of all muscles, always pro- 

 ceeding more slowly than that of the increasing energy before the 

 maximum. 



The muscles of the unicellular Infusoria, no longer doubtful in a 

 physiological sense, show us muscle as a constituent of the cell, and 

 differentiation, without the production of new cells specially endowed 

 for the purpose, taking place in one cell to the extent of elaborating 

 contractile elements determinate in form and precise in work. It is 

 very noteworthy that side by side with these muscular strips provided 

 with highly regulated movement, other protoplasm persists, which 

 continues uninterruptedly its ordinary unordered movements, while 

 no such unrest is to be remarked in the muscles. On the contrary, 

 these latter are only used from time to time, apparently for attaining 

 distinct objects. We get the impression that the automatism has, as 

 it were, been lost by this portion, so that it must wait for stimuli to 

 reach it from other parts of the cell. If oxygen really applies the 

 first spur to the protoplasm, it has no direct power over the primitive 

 muscle, so that compared with the protoplasm the muscle is endowed 

 with a diminished irritability. 



It has often been said that protoplasm presents the complete set of 

 vital phenomena — assimilation, dissimilation, contractility, automa- 

 tism, resorption, respiration, and secretion, and even reproduction by 

 dividing. Leaving reproduction on one side, as now disputed and on 

 good grounds, we can assent to the assertion, and examine which of 

 those functions remain for the products of differentiation. In the case 

 of the muscle, we f nd it to be all of them with the exception of a 

 single one ; for, while it undoubtedly takes part in nutrition as in 



