260 Dr. Beale Croonian Lecture. [May 11, 



invariably the case, numerous terminal organs exist, these are always 

 connected together by nerve-fibres which pass from one to the other. 

 Although the arrangement is not always so distinct as represented in this 

 drawing of the papillae from the tongue of the frog, I always find that 

 where a nerve-trunk divides into two sets of branches, there exists at the 

 point of division a fibre or fibres which seem to connect the two terminal 

 organs to which the bundles of fibres pass. Passing to every touch-body 

 in the papillae of the skin of the finger, I find more than one nerve- 

 fibre ; and the corpuscle itself seems to consist of a very much coiled 

 and reduplicated nucleated nerve-fibre, as represented in this drawing. 



In the peripheral cutaneous nervous organs of many invertebrate animals 

 which I have examined, especially in some of the insects and annelids, I 

 find a bundle of nerve-fibres, not a single nerve-fibre, as is usually repre- 

 sented. This drawing illustrates the view generally entertained ; and this 

 one, my own inference of the structure of these organs. Even in the 

 Pacinian body I find no such indications of a true termination of the axis- 

 cylinder as is usually described : not only so, but in many cases 1 have 

 seen three or four very wide lobe-like continuations of the axis-cylinder 

 bending downwards from its highest point, and passing apparently into 

 very fine granular fibres which lie between the laminated capsules, and are 

 continued into the nerve-sheath. The drawing will illustrate the struc- 

 ture of all these allied peripheral nerve-organs, according to my observa- 

 tions. 



Evidence in favour of continuous nerve-circuits, derived from the study of 

 the development of nerve-fibres distributed to muscle. 



The development of nerves distributed to muscle is most difficult to 

 investigate, but it is a subject well worthy of most attentive study ; and 

 although I cannot hope to give a clear account of the process, I shall make 

 an attempt to describe what I have myself seen. The relation of nerves to 

 the contractile tissue of muscle and other tissues, and the general arrange- 

 ment of nerve-fibres, having been determined, one cannot avoid asking how 

 the fibres became arranged as we see them in the fully formed texture. 



Of the part taken by the masses of germinal matter there cannot be the 

 slightest doubt ; for it can be shown most conclusively that as the nerves 

 advance from the early to the complete stage of their development, the 

 distance between the several masses of germinal matter gradually increases. 

 This may be proved in the case of dark-bordered as well as of "very fine 

 nerve-fibres. It is well shown in these figures. At an early period of 

 the development of muscle, very numerous masses of germinal matter are 

 seen amongst the muscular fibres, in which transverse markings are already 

 developed. These, as I have been able to satisfy myself by researches 

 upon the diaphragm and intercostal muscles of the foetal dog, are con- 

 cerned in the formation of nerves and capillaries. 



In the young caterpillar the surface of some muscular fibres seems to be 



