180 
G. H. F. Nuttall and D. Ketlin 
integument, the insect should be released by the fingers, whilst it remains im¬ 
paled on the pipette point. The operator now places the free end of the pipette 
between his lips and blows some of the fluid it contains into the insect’s body 
cavity. As soon as this is accomplished the louse is detached from the pipette 
by sliding a needle along the glass. The insect, after resting on cloth at room 
temperature for an hour, is fed and afterwards returned to the thermostat. 
After 20-24 hours, if the louse has been injected with ammonia-carmine, the 
nephrocytes of the living specimen are found to be coloured red when viewed 
by transparency. 
We would remark that before reaching conclusions regarding experiments 
of this character it is necessary to confine one’s attention solely to the living 
insects because more or less generalized coloration may take place in dead or 
dying lice. 
Results of Intra-coelomic Injections of ammonia-carmine in Pediculus. 
Of 22 experimental injections of the foregoing description carried out by 
us on Pediculus humanus, 14 gave good results. The failures were due either 
to the lice being injured through laceration of the gut or through precipitation 
of the injected carmine having occurred. The successfully treated lice were 
killed for purposes of examination 3-5 days after injection. One specimen (?) 
injected on 4. vi. 1918, which showed coloured nephrocytes after 24 hours, 
survived until 21. vi, when she was killed. In other words she lived for 16 
days, and laid 62 eggs during this period, her nephrocytes remaining coloured 
throughout. It is evident therefore that the technique when successful does 
not involve material injury to the louse. 
When the lice are examined 24 hours after injection no traces of ammonia- 
carmine are visible in the perivisceral fluid, on the other hand all the nephro¬ 
cytes are found to be coloured red. When the lice are immersed in water and 
slightly compressed between slide and cover-glass, being viewed dorsally with 
the binocular microscope, the exact distribution of the nephrocytes can be 
clearly discerned. As shown in Fig. 4, as a rule, two red peri-oesophageal 
agglomerations of nephrocytes are visible, at times the masses are fused in 
the form of an irregular crescent. 
Apart from the foregoing, small groups of red cells are seen irregularly 
distributed beneath the dorsal surface. The distribution of these cells varies 
in different individuals and in one and the same individual according to its 
state of repletion, or if the specimen is a female, according to the state of 
development of the ova. These cells or groups of cells, when dissections are 
made, are' seen to be united to the fat body as shown in Fig. 5, and they 
correspond in every way to the cells we have already described as dorsal or 
disseminated nephrocytes. When examined under a high power, they exhibit 
the two characteristic nuclei which are hidden in the illustration through the 
accumulation of carmine granules within the cells. 
