IO5O VERTEBRATED ANIMALS 



other hand, the surface of the fibre be brought into focus, the convex 

 ribbings appear light and intervening depressions dark, which is the 

 aspect originally represented by Bowman. The appearances are the 

 same in the extended and contracted states of the fibre ; with the 

 exception that the alternation of light and dark strife is closer in the 

 contracted state, while the breadth (representing the thickness) of 

 the fibre is correspondingly increased. 1 It is well none the less in 

 the present state of our knowledge to refrain from conclusions as to 

 the absolute structure of the striated fibrilla?. It ranges itself, from 

 the modern microscopist's point of view, with other striated objects, 

 and will require the possession of lenses of a N".A. twice or thrice that 

 of those which are now within our reach. There is no immediate pro- 

 spect of these, it is true ; but they cannot be considered impossible 

 by the student of the past history of microscopy 



In the examination of muscular tissue a small portion may be 

 cut out with the curved scissors ; this should be torn up into its 

 component fibres ; and these, if possible, should be separated into 

 their fibrillse by dissection with a pair of needles under the simple 

 microscope. The general characters of the striated fibre are admi- 

 rably shown in the large fibres of the frog ; and by selecting a 

 portion in which these fibres spread themselves out to unite with a 

 broad tendinous expansion, they may often be found so well dis- 

 played in a single layer as not only to exhibit all their characters 

 without any dissection, but also to show their mode of connection 

 with the ' simple fibrous ' tissue of which that expansion is formed. 

 As the ordinary characters of the fibre are but little altered by 



*/ - 



boiling, recourse may be had to this process for their more ready 

 separation, especially in the case of the tongue. Dr. Beale recom- 

 mends glycerin for the preparation, and glycerin media for the 

 preservation, of objects of this class ; and states that the alternation 

 of light and dark spaces in the fibrilhe is rendered more distinct by 

 such treatment. The fibrill;e are often more readily separable when 

 the muscle has been macerated in a weak solution of chromic acid. 

 The shape of the fibres can only be properly seen in cross-sections ; 

 and these are best made by the freezing microtome. Striated fibres, 

 separable with great facility into their component fibrilla?, are 

 readily obtainable from the limbs of crust; i< v.-i .-md of insects; and 

 their presence' is also readily distinguishable in the bodies of worms, 

 even of very low organisation ; so that it maybe regarded as charac- 

 teristic of the articulated series generally. On the other hand, the 

 molluscous classes art 1 , for the most part, distinguished by the non- 

 striation of their fibre ; there are. however, some exceptions, such as 

 the muscles of the odontophore in the snail and the powerful adductor 

 muscle of J*ecten. Its presence seems related to energy and rapiditx 

 of movement, the non-striated presenting itself where the move- 

 ments are slower and feebler hi their character. 



The 'smooth' or unit striated form of muscular fibre, which is 



1 (Jinn-/. Jouni. Jl/"/Vn>.sr. ,SVv. n.s. \\i. p. 307. More recent views will be found in 

 .Mr. C. K. iU.ai'shiillV |iii|>er in vol. \\viii. of the same journal, and in the memoirs 

 cited by him. The subject is one which will doubtless lon^r occupy the attention of 

 the 



