On the development of Filaria sanguinis hominis, and on the mosquito considered as a nurse / by Patrick Manson.

  • Manson, Patrick, Sir, 1844-1922.
Date:
[1878]
Catalogue details

Licence: Public Domain Mark

Credit: On the development of Filaria sanguinis hominis, and on the mosquito considered as a nurse / by Patrick Manson. Source: Wellcome Collection.

    10/16 (page 308)
    equivalent to about one drop of bloed from tbc man on whom most of my observations were made, would contain from ten to thirty Hsematozoa; whereas the blood drawn by a single mosquito, about as much as would fill one slide only, contained from twenty to thirty as a rule, and sometimes many more. One slide, in which I had the curiosity to count them, had upwards of a hun¬ dred and twenty specimens. From this it would appear that the mosquito has the faculty of selecting the embryo Eilarice ; and in this strange circumstance we have an additional reason for con¬ cluding that this insect is the natural nurse of the parasite. All Embryos do not attain maturity.—By far the greater number die and are disintegrated, or are expelled in the faeces undeveloped. At the end of the third, fourth, or fifth day, when the stomach is quite empty as far as food is concerned, and an embryo could not easily be overlooked, only from two to six are found in the same or slightly different stages of the metamorphosis, which I will now attempt to describe. The Metamorphosis of the Embryo.—The embryo for a short time after entering the stomach of the mosquito retains all the appearances and habits which characterized it when in the human body; that is, it is a long snake-like animal, having a perfectly transparent structureless body enclosed in a delicate and, for the most part, closely applied tube, within which it shortens and ex¬ tends itself, giving rise, from the collapse of the tube when the body is retracted at either end, to the appearance of a lash at the head and tail. In a very few hours changes commence. The tube first separates from the body by an appreciable interval, giving the appearance of a distinct double outline, and the body itself becomes covered with a delicate but distinct and closely set transverse striation. Oral movements are now very evident, not that they did not exist before, but because the slight increase of shading from the striation renders them more apparent. The indication of a viscus seen in some specimens vanishes at this stage. Presently the tube or sheath is either digested by the gastric juices of the mosquito; or it is cast off as a snake does its skin, and the animal swims about naked, and without any trace of a head- or tail-lash. The striation becomes verv marked ; but •/ ! gradual^ as the blood thickens, and the movements of the em¬ bryo become in consequence less vigorous, these markings com¬ pletely disappear, giving place to a peculiar spotted appearance. Bach spot is dark or luminous, according to the focusing of the