on the Structure of the Muscular Fibril. 369 



they do not show that views thus long since published require 

 an essential change. 



A friend, long accustomed to use the microscope, and gifted 

 with a keen microscopic eye, whom I had convinced of the 

 existence of spirals in muscle, once suggested that the spiral 

 structure might " be the earlier rather than the fully- developed 

 condition of the fibril, the quadrilateral particles representing its 

 fully-formed state." Referring him to the drawing reproduced 

 in fig. 1, I was compelled, with almost rude brevity, to say that 

 I should find it about as easy to admit that thread exists before 

 the flax that forms it, or a chain before the links of which it is 

 composed. 



Consisting as it does of two spiral filaments, the muscular 

 fibril, in its movements between contraction and relaxation, of 

 course presents a variety of forms. And as the microscopic in- 

 quirer into the structure of muscle is sure to have one or more 

 of such forms before him (unless all the muscle in the field of 

 view is in full contraction or complete relaxation), I have con- 

 structed models by which the eye may be prepared for these 

 forms. 



In fig. 6E is shown a very simple method of constructing such 

 a model. At a are two lead wires of equal length, which, held 

 parallel and together, were obliquely wound upon a large knit- 

 ting needle, b. The needle having been withdrawn, there re- 

 mained a model of the mature and acting muscular fibril (and 

 indeed of the original form of all organic fibre) . So easily did 

 the two wire spirals then change their positions, that on merely 

 rolling the model on a white surface, I saw it present the three 

 varieties of form a, b, c, drawn from nature in fig. 7 ; which in- 

 clude two states of the single and one of the double cylinder. 



While, however, from their weight, wires of lead have the ad- 

 vantage just mentioned of presenting changes in relative position 

 on the model being simply rolled, they are not elastic. I there- 

 fore used wire of gutta percha, fig. 6 F. At a in this figure is a 

 bit of small wire of gutta percha. This I bent upon itself at c ; 

 and then, having firmly tied with thread the loop c to a knitting 

 needle b } I wound the double wire upon the needle in a direction 

 almost as nearly transverse as possible. Then, keeping firm 

 pressure applied by the finger and thumb at the lower ends of 

 the wires, I plunged the wires for a few seconds into water of 

 about 130° Fahrenheit (44° Reaumur*). Thus softened and 

 deprived of their elasticity, the wires were slipped off the needle. 



* If the water be too hot, the wires over-softened adhere together. 



