T. GooDEY 37 



Examination of the sections from the tail and one of the feet failed 

 to reveal any sign of skin infection. 



(3) A young mouse (body about 1 inch long) was chlorofoi-iucd and 

 the skin from the abdomen and flanks removed. This skin was stretched 

 and pinned over a hole about ^ inch in diameter in the centre of a piece 

 of sheet cork j% inch in thickness. The cork was then floated on the 

 surface of some N saline which had previously been warmed up to 

 37° C. and placed in a glass jar 3 inches high by 2^ inches in diameter, 

 having a well-fitting stopper. The cork floated near the top of the jar 

 and care was taken that the warm saline came into contact with the 

 underside of the skin by first allowing the bubble of air to escape from 

 between the skin and the cork. The jar could be placed on the stage of the 

 binocular dissecting microscope and the surface of the skin easily examined. 



A drop of water containing a large number of active larvae was placed 

 on the skin. Immediate examination showed them to be actively moving 

 in the drop. The jar was placed in the incubator at 37° C. and examined 

 every quarter of an hour during a period of one and a half hours. During 

 this time some of the larvae could be seen moving very sluggishly amongst 

 some threads of blotting-paper in the drop, whilst others moved more 

 actively. As far as could be seen there was no down-boring motion 

 exhibited by the larvae and no sign of skin penetration. At the end of 

 an hour and a half the bulk of the supernatant water of the drop was drawn 

 o& by means of a capillary pipette, and a drop of fresh white of egg was 

 placed on the skin. Examination under the microscope showed the 

 larvae moving in this. The albumen was then coagulated by dropping 

 hot 90 per cent, alcohol on to it from a pipette. This was done so as 

 to fix in position the larvae which had been added with the original 

 drop of water. The skin was then immersed in 10 per cent, formalin for 

 fixation. It was later on treated in the usual way and embedded in 

 paraffin for sectionising. Examination of the stained sections failed to 

 reveal any sign of skin infection, though many slides showed sections 

 of larvae between the coagulated albumen and the epidermis. 



I realised that in the above described experiments I had, quite 

 possibly, not brought about the conditions requisite for the larvae to 

 penetrate the skin, i.e. conditions under which known skin penetrators 

 such as the larvae of Ancylostoma duodenale or Necator americanus 

 would act. I therefore determined to obtain a culture of the eggs of one 

 of these forms and rear a number of the ensheathed larvae with a view 

 to finding out the exact experimental conditions required by these for 

 skin penetration. 



