50 Mr. C. E. Walker and Miss A. L. Embleton. [Jan. 16, 



were done, but these will not be given in detail as the results were exactly 

 the same as has already been described. 



Experiment 12. Nerve Muscle Preparation of Frog. Pithed Frog. — The 

 preparation was made in the usual way. An induced current was used to 

 stimulate the nerve. The solution of poison was applied to the muscle with 

 a brush. Each time the poison was applied the muscle shortened slightly. 

 The muscle was kept moist with the solution of poison until it failed to 

 contract, when the nerve was stimulated. The electrodes were now applied 

 to the muscle itself, but it failed to respond with the strongest current. 



On the Origin of the Sertoli or Foot-cells of the Testis. 



By C. E. Walker, Assistant-Director of Cancer Kesearch Laboratories, 

 University of Liverpool, and Alice L. Embleton, B.Sc 



(Communicated by Dr. C. S. Sherrington, F.R.S. Received January 16, — 

 Read February 1, 1906.) 



[Plates 5 and 6.] 



The function of the Sertoli or foot-cells of the mammalian testis has 

 frequently been described, and will not be dealt with in the present brief 

 communication. Neither do we intend to deal with the later stages of the 

 life-history of these cells, except in so far as to draw a parallel between them 

 and the cells performing a similar function in the amphibia. 



In the embryo testis of a mammal before the tubules are formed it 

 is seen that a number of so-called male ova lie, singly or in groups of 

 about four, among masses of cells, which we will for the moment designate 

 as being of a more or less undifferentiated character. These undifferentiated 

 cells are much smaller and of quite a different character to the male ova 

 (see fig. 1). 



At a little later stage we find that the wall of the tubule begins to 

 appear. This wall is apparently actually in process of formation in parts 

 of fig. 1, while in fig. 2 a tubule with a complete wall has been formed. 

 We are convinced from a careful study of the stages of development that 

 cells which form the wall of the tubule and those that are enclosed with 

 the male ova inside the wall thus formed are identical or derived from the 

 same immediate ancestors. As development goes on these cells become 

 more and more differentiated until we reach the state of the tubule in the 

 adult testis (fig. 3). 



