TRANSACTIONS OF THE SECTIONS. 83 



and we are occupied now in investigating their mode of formation and connexion 

 with one anotlier. There seems much reason to think tliat they are more closely 

 related, more continuous, than we have been in the habit of regarding them. There 

 is now little doubt of the continuity of the nerve-fibres and the nerve-vesicles ; and 

 it is not improbable that the other parts of the nerves are continuous with the 

 several tissues among which they ramifj^, with the deeper prolongation of epithe- 

 lium, with the elementary structure of muscle, and with the filaments of areolar 

 tissue. The continuity of the areolar tissues with serus, fibres, and mucus mem- 

 brane on the one hand, and with the intimate structure of the various organs on 

 the other, is more clearly shown, and a very general and extensive continuity is 

 thereby established. The cornea is continuous with the sclerotic, and so with the 

 speri sheath and dura mater. Even epitheliimi, which we were wont to regard as 

 a distinct external and easily separable sheath, is found to send its filamentary 

 prolongations into the subjacent organs, wliich become blended with the areolar 

 and nervous and perhaps with the lymphatic systems. The epithelium of the 

 glandular tubes is in some organs imdistinguishable from the cells which occupy 

 the stigma. The blood-vessels in many animals are continuous with the areolae of 

 the tissues ; and in all, the ultimate circulation take place through the tissues, the 

 nutritious fluid passing freely to and fro between their interstices and the interior 

 of the capillaries where capillaries are present. We are thus reminded of the fact 

 that in their embryonic period the several structiu-es, or the potential rudiments 

 of them, were all blended in a homogeneoiis germinal mass ; and we learn that 

 though they have become differentiated they have not become separated, but re- 

 tain in their mode of connexion the traces of their common parentage and of 

 their early continuity. Such a blending of ultimate tissue, as a remnant of em- 

 brj'onic condition, assists ns to explain many things, such as the transfer of im- 

 pressions and what we call sympathy, that are at present difficult to imderstand, 

 and is an additional illustration of the simple method by which, in nature's works, 

 great ends are attained. 



We perhaps scarcely realize and appreciate the bearings of the fiict that all the 

 various tissues are formed from a primitive homogeneous and continuous plesina, by 

 the formation and separation from one another of " portions," "centres," " masses," 

 "cells," or whatever we please to call them, and their development into structure ; 

 attention has been directed almost exclusively to the formation and development 

 of these masses and too little to their separation, though the latter is a process 

 little, if at all, less important than the former, and must be eft'ected by something 

 analogous to what we call abruption. Indeed the work of abruption, or hollowing 

 out, during the embryonic state is little less active than that of secretion or building 

 up. We are familiar with its work in the formation of the areolae and cavities of 

 bone, in the removal of the parts of the iris and eyelids that do not become deve- 

 loped into permanent structure ; but we are not perhaps sufficiently impressed with 

 the fact that the various cavities, canals, and spaces in the interior of the body are 

 due to the same progress, and that the failure or arrest of it may be the cause of 

 many of the so-called adhesions of seams and other surfaces, of the imperforate con- 

 dition of canals, and the union of parts that should be free. The transition from 

 the investigation of the fine processes of the animal organism to the consideration 

 of the forces by which they are brought about is a natural, a necessary step, though, 

 I need scarcely say, it takes us into a region where advance must be slow and 

 where difficulties seem almost insurmountable. We are probing more into the very 

 deepest recesses of nature, and inquiring into her closet secrets. We feel om'selves 

 here almost to be 



" Children crying in the darkiiess, 

 Children crying for the light, 

 And with no language but a cry." 



Yet cry we must, and in time we shall get some, though perhaps never a full replj-- ; 

 indeed when the questions that here arise shall have been fully answered, when 

 man shall be entirely satisfied as to the essential nature and the first causes of that 

 which he sees, when these deep problems shall be worked out, when the penetralia 

 of nature's temple shall be thoroughly explored, science vrill have told its tale, and 

 the physical world will cease to afford its arousing interest for ns. Of such satiety 



6* 



