MALARIA EXPEDITION TO NIGERIA 
73 
The Anatomy of the Mouth parts of the Female Anopheles Costalis 
The discovery of the final stage of the metamorphosis of the larval stage of 
F. nocturna in sections of the proboscis of mosquitoes, by Low, 1 in 1900; the 
observations of James 2 as to the way in which the matured larvae tend to travel 
through the tissues of the head and neck into the proboscis ; the work of Grassi 3 
on F. immitis in the dog, and in Anopheles claviger, in which the larvae were found in 
the labium ; and our own researches in West Africa on the life history of F. nocturna in 
the body of Anopheles costalis ; make a knowledge of the minute anatomy of the 
proboscis of the mosquito requisite for an exact understanding of how the larva 
leaves the insect and is transmitted to man. 
As far as we have been able to ascertain very little has been done by 
entomologists in this country in the investigation of the histology of the proboscis of 
the mosquito ; it has chiefly been examined from a morphological point of view, as 
of importance in the classification of species. 
Methods of investigation employed 
1. Examination of the proboscis of living insects. 
2. Dissection of specimens in the fresh condition ; and the examination of 
the organ hardened in alcohol and cleared in oil of cloves, and mounted as a whole or 
in parts in Canada Balsam. 
3. By sections. Mosquitoes were killed by chloroform vapour ; hardened in 
absolute alcohol for one or two hours, and embedded in paraffin. Serial sections 
(6 to 10 u thick) of the proboscis and head were cut in three directions. Thin 
paraffin sections of the proboscis are with difficulty fixed to a slide by the ordinary 
methods of laboratory practice ; the chitinous skeleton tending to break away from 
the delicate tissues which it encloses, in the processes of the manipulation of paraffin 
sections, so that minute anatomical relations become disturbed and obscured. 
By the use of a slight modification of ObregiaV method for fixing sections 
cut in paraffin, we were able to secure excellent results. A mixture of two parts of 
commercial liquid glucose and one part of a thick syrup of pure dextrin* is spread 
in a thin layer on to the glass slide by means of a glass rod. The serial paraffin 
sections as they are cut are laid directly on this layer on the slides, which are then 
placed in an incubator at about 40 0 c. for some hours, until the glucose mixture has dried 
hard. The paraffin is then removed by means of xylol and the slide with the 
sections is passed through absolute alcohol. A solution of photoxylin is then poured 
over the slide, so as to form a thin film over the sections ; this layer of photoxylin is 
1. Low, British Medical yournal, 1900. June 16. 
2. James, British Medical Journal, 1900. Vol. ii, Sept. 1, p. 535. 
3. Grassi, British Medical Journal, Nov. 1900. 
4. Ohregia, Neurologisches Centralbiatt, 1890. 
Gultahd, Journal of Pathology, Feb. 1893, p. 391. ~ 
16 oz. dextrirr ; 17J oz. water ; 15 grains thymol. 
K 
