396 THE ANIMAL PARASITES OF MAN 



(4) Fix in alcohol. 



(5) Stain with azur II, i in 1,000. Differentiate as above. Examine 

 as a dry film. This method suffices for showing the excretory cell and 

 the Gi cell ; or 



(6) Stain with haematein (slightly steaming), especially for the 

 column of nuclei and the sheath. The fixation in alcohol in this 

 case may be omitted. 



(7) The removal of the haemoglobin and the fixation may be 

 combined by using Ruge's mixture (formalin 2 per cent., containing 

 i per cent, acetic acid) or acetic alcohol (glacial acetic i, alcohol 3). 1 



Structure of Larvce. (i) Subcuticular cells : By vital staining, at 

 intervals underneath the cuticle are seen a series of spindle-shaped 

 cells the subcuticular matrix cells of Rodenwaldt, the muscle cells 

 of Fiilleborn. There are thirty or forty or more of these. 



(2) Nerve ring : Appears as a break in the nuclear column about 

 20 per cent, of total length from the head. 



(3) Excretory system : Consists of a lateral spherical hollow 

 excretory pore which shows a radial striation. Connected with the 

 pore is an excretory cell which appears to be canalized. Excretory 

 pore, 29'6 per cent, of length from head. Excretory cell, 30*6 per cent, 

 of length from head. 



(4) " Genital " cells and anal pore : Consists of a pore opening 

 ventrally on a very fine papilla with which are connected four 

 other cells in series, the chief " genital " cell (Gi) being some distance 

 from the three others, which lie close to the pore. Gi, 70^6 per cent., 

 anal pore, 82-4 per cent, of length from head. 



(5) Internal body, viscus, or reserve material : Best shown by vital 

 staining with neutral red. This is a granular strand-like body extend- 

 ing from 527 per cent, to 65 per cent, of length from head. 



(6) Tail end : (i) Rod-like structures resembling those in the head, 

 90 per cent, of length, (ii) The column of nuclei extends to 95 per cent, 

 of length, so that the terminal portion is free from nuclei. 



(7) Mouth : Terminal according to some authors, lateral according 

 to others. Some describe a fang on the head, others not. By vital 

 staining and eosin differentiation two rod-like structures with mush- 

 room-like caps can be seen behind the head. 



(8) Cuticle : Transversely striated. There is a longitudinal break in 

 the striation on each side corresponding to the lateral lines. The stria- 

 tion is best shown by vital staining with azur II and eosin differentiation. 



(9) Column of nuclei : These nuclei of the gut cells form the 

 main feature in ordinary dry films stained with haematoxylin. They 

 are separated by a space from the subcuticular cells. 



1 [Acetic alcohol does well for detecting crescents in thick films of malaria blood. 

 J. W. W. S.] 



