266 Dr. Beale Croonian Lecture. [May 11, 



an extension from each of these to distant parts took place, it must follow 

 that the portion first formed would be the oldest; but all observation seems 

 to show that development gradually goes on in different and distant parts 

 at the same time. And I infer that in the process of regeneration of the 

 lobster's claw, or of the lizard's tail, of the fully formed animal, the several 

 tissues constituting the organs are entirely developed anew from a formless 

 mass, and not by the simple extension of the tissue of the muscles, nerves, 

 vessels, &c., which exist in the stump. In the first instance there results 

 a soft material, which exhibits no indications of definite structure ; and as 

 development proceeds, the masses of germinal matter taking part in the 

 development of nerves are seen arranged in lines, and are continuous with 

 those in the nerves of the stump. It is, however, possible that new masses 

 of germinal matter may grow and multiply from these latter and extend 

 into the soft indefinite tissue first produced and destined to serve only 

 a very temporary purpose ; but, before I can consider this question advan- 

 tageously, I must make further observations. And it appears from ob- 

 servations in the case of the frog, that when a new peripheral part or 

 organ is developed, new central nerve-cells are developed in connexion with 

 it. And it is probable (indeed it appears to me certain) that even in man 

 this development of new central and peripheral organs goes on in certain 

 instances. For example, at each pregnancy in the human female, it is pro- 

 bable not only that new muscular fibres, vessels, nerves, &c. are developed 

 in connexion with the growing uterus, but that new nerve-centres are also 

 produced, with which the new nerves are connected ; and I regard it aa 

 most probable that during the development of the lizard's tail and lobster's 

 claw new central nerve-cells in connexion with the new nerve-fibres are 

 developed in the already existing but comparatively simple nerve-centres. 



Of the relation of the ultimate branches of the nerve-fibres to the elements 

 of the tissue and to the germinal matter. 



In no case does the nerve become continuous with any part of the con- 

 tractile tissue of muscle ; nor is it connected with the nucleus of the mus- 

 cular fibre or with that of any other tissue. 



The ultimate nerve-fibre bears the same relation to the contractile tissue 

 of muscle that it bears to fibres of white fibrous tissue, to cells generally, 

 and to the processes of cells, such as the prolongation from the pigment- 

 cells of the frog, those of the corneal corpuscles in the cornea, &c. The 

 arrangement is such as would lead us to infer that the tissue is influenced 

 by the current passing through the nerve, not by any change involving an 

 anatomical continuity of structure from the nerve to the tissue affected by 

 it, or even in actual contact with any part of it ; for in very many instances 

 we can prove that the nerve is not in very close contact with the tissue it 

 influences. Moreover, results resembling those which occur from the action 

 of a nerve may be brought about by the passage of a current of electricity 

 through a wire situated at a considerable distance from the muscle, and 



