90 Dr. Early's renewed Inquiries concerning the 



threads, to gain a greater length; but being prevented from 

 doing so by the hinderance above supposed at their ends, they 

 seek to gain that greater length through lateral inflexions, which 

 in such a case must produce a zigzag form. Were an antagoni- 

 zing force apphed, the elongation could follow without the for- 

 mation of such zigzags. 



We are indebted to Prof. Bowman for many microscopic 

 measurements of the primitive fasciculi in difi"erent classes of 

 animals. He found the largest in Fishes ; they had a less size 

 in the Amphibia, were smaller in Mammals, and smallest in 

 Birds. Bowman's measurements are veiy munerous, and were 

 no doubt made with the greatest care. He has, however, omitted 

 to draw general conclusions therefrom, and makes no remark as 

 to the cause of those differences in size. The author in this 

 respect follows the example of Prof. Bowman. He brings for- 

 ward no general conclusions of his own on the subject, and indeed 

 for this reason : because he thinks that we ought first to have 

 determined the mean size of the primitive fasciculi in the same 

 individual as well as in different individuals of the same species, 

 according to their different manifestations of activity, before we 

 undertake to draw general conclusions. Yet he cannot refrain 

 from here pointing to the following fact, mentioned in a former 

 part of his memoir. According to his obsei-vations, the primitive 

 fasciculi are at first merely double spirals, i. e. they are no other 

 than fibrils. The metamorphosis of fibrils into primitive fas- 

 ciculi is especially observable in the heart, where the young 

 fasciculi are found, at first flat and scarcely broader than the 

 fibrils themselves. The cause of these continued changes in the 

 muscle of the heart, as already said, it may well be supposed is 

 no other than the ceaseless activity of that organ. Scarcely is it 

 to be doubted that the same thing takes place in other muscle 

 also, though more slowly. (Certain muscles are then referred 

 to as affording examples of great activity, and it is remarked 

 that in different individuals of the himian race the primitive 

 fasciculi in the muscle of certain parts are probably unusually 

 small.) Hence it occurred to the author to offer the following 

 remarks concerning the measurements of Bowman. In Fishes 

 the primitive fasciculi were found the largest, because of the low 

 degree of muscidar activity required in the element in which 

 they live (though perhaps the muscles of the fins and gills may 

 be here excepted, and it is known that they present even exter- 

 nally an appearance different from that of the other muscles). 

 In Birds, on the contrary, the primitive fasciculi were found 

 the smallest, as was to be expected from the high degree of 

 muscular activity of this class. Amphibia and Mammals pre- 

 sented a middle average size, from their muscular activity occu- 



