369 



shown by studies upon tne development of this tissue, which 

 occurs by large, nucleated cells being arranged in rows, then 

 fusing together, forming cylinders ; these last are the fibres 

 proper, and they may be unstriated, constituting the muscles 

 of organic life, or they may be striated, forming the voluntary 

 muscles, according to the degree of development they attain. 

 The muscle of organic life is but a lower, and, in one sense, un- 

 developed form of that which is striated. Striated muscle stands 

 at the head of this tissue, and there may be a degradation from 

 this all the way down to the Bryozoa and worms, where this 

 tissue occurs even without fibres, there being only colligations of 

 granules under peculiar forms. It may be here remarked that 

 in Alcyonella (of the Bryozoa) I have failed to find striated 

 muscle, after repeated search, although Allman, of England, 

 declares that he has observed it in the Bryozoa, and especially 

 in Paludicella ; but it may be mentioned that in the lower ani- 

 mals there may be often seen a ruffling of the muscular tissue, 

 which, at first, resembles the appearance of striation. 



In the higher animals, all voluntary motion is performed ex- 

 clusively by means of the striated muscular tissue; but in the 

 lowest forms, non-striated muscle must subserve the same pur- 

 pose ; thus, the Acalephce, whose muscles are all non-striated, 

 move at will, and, according to circumstances, their various 

 appendages. The histological condition of striation would 

 appear to be intimately connected with rapidity, delicacy, and 

 definiteness of action, a point well illustrated in the structure 

 of the wing-muscles of the musquito. 



In illustration of Dr. Burnett's remarks, several micros- 

 copic specimens, prepared by Dr. Durkee, were exhibited. 



One specimen, from a human embryo, weighing seventy grains, 

 showed the arrangement of the primitive cells in a linear series; 

 another specimen, from the same subject, displayed the cells 

 united, the nuclei being separated and somewhat broken up, and 

 the longitudinal lines just beginning to be developed. 



A specimen was also exhibited to show the relative size of the 

 perfect elementary muscular fibre in the adult subject, when 



PROCEEDINGS B. S. N. H. 24 APRIL, 1854- 



