August 1, 1891.] 



KNOWLEDGE 



143 



Mosquitos has been made out in recent years. It is well 

 known that there is a class of worm-like creatures, differing 

 from the earthworm and other similar animals in not 

 having the body divided into a series of rings, that inhabit 

 various parts of the bodies of vertebrate and other animals. 

 Man is subject to the attacks of several parasites of this 

 sort, and shares them with other animals — i.e., the para- 

 sites pass through their early life in the body of one host, 

 and their later life in that of another. Numerous experi- 

 ments and investigations, by Dr. Manson and others, 

 seem to have proved that such a connection exists between 

 man and a particular kind, or some few kinds, of Mosquito. 

 The parasite is called FiJaria mwjuinis hominis (the thread- 

 worm of the blood of man). The adult female of this 

 creature inhabits the lymphatic glands of man, and is 

 the cause of the curious and repulsive disease called 

 elephantiasis, and of kindred maladies. Embryos produced 

 from these sexually mature forms, pass from the lymphatic 

 system into the blood of man and circulate with it, causing 

 in this stage certain kidney diseases. No forms inter- 

 mediate between these two have been found in man, and 

 it is therefore evident that the intervening stages of the 

 life of the parasite, whatever they may be, are spent else- 

 where. From the blood of man, the embryos pass into 

 the body of the Mosquito as it sucks its victim. Only a 

 few of these seem to be digested with the blood ; the rest 

 escape from the Mosquito's digestive tube and establish 

 themselves in its thorax, at the same time undergoing a 

 change of form indicative of an advance in development. 

 Thus far the history of the parasite has been traced, but 

 exactly what happens afterwards is still to some extent a 

 mystery. The Mosquito infested with FilariiE appears 

 soon to die, the parasite apparently subsisting on the 

 contents of its thorax. It has been thought that the 

 Mosquito's body falling into the water on its death, the 

 parasites escape and pass a free existence for a time, being 

 after a while re-introduced into a human host by the 

 drinking of the water that contains them. In investigating 

 these facts. Dr. Manson got a Chinaman whose blood was 

 known to contain Film-iir to sleep in a small curtained 

 chamber placed in a larger room in which Mosquitos were 

 flying. The door of the " Mosquito house" having been 

 left open for some hours after the man had gone to sleep, 

 was then closed, and the Mosquitos which had entered 

 were thus entrapped. These were found in the morning 

 clinging to the netting, gorged with blood, and were care- 

 fully collected day by day, and preserved ; some were 

 examined under the microscope at once, others not until 

 after an interval, so as to secure a later stage of the 

 parasite ; in this way, by the examination of large numbers 

 of the insects, after intervals of dift'erent length, the 

 fate of the swallowed Filariir was at length made out up 

 to the point indicated above. 



One of the most curious of the annoyances that have 

 been recorded as occasioned by Gnats was illustrated in 

 some specimens exhibited at a meeting of the Bristol 

 Naturalists' Society in 1878. Mr. J. W. Clarke showed 

 some sheets of writing paper from Sweden which formed 

 part of a large consignment that had been greatly injured 

 during the process of manufacture through a swarm of 

 Gnats having got mixed up with the pulp. The remains of 

 the flies were to be seen in the material of the paper, and 

 some specimens were so perfect as to be easily identified as 

 a Cuh'.r, and all seemed to belong to the same species. 

 Another record is made of a Centipede similarly preserved 

 in paper, and no doubt paper manufacturers could supply 

 many others, though perhaps few on so extensive a scale as 

 that alluded to above. 



(To be continued.) 



THE LIFE-HISTORY OF FILARIA SANGUINIS 

 HOMINIS. 



By Joseph W. Willi.uis. 



THE curious parasite, whose life-history we are 

 about to relate, is found in the blood of persons 

 suffering from a disease termed chyluria, which is 

 characterized by the presence of chyle in the urine, 

 and which occurs in certain tropical and sub- 

 tropical countries, especially in Brazil, Mauritius, the Isle 

 of Bourbon, Bombay, the West Indies, South Carolina, 

 and Queensland. Cases now and again occur in Europe — 

 one such came under my notice two years ago in a native 

 of India — but, in the majority of instances, the persons 

 affected have visited the tropics at some period of their 

 lives. Five cases are, however, known to have occun-ed 

 sporadically, and out of these two have been recorded in 

 England — one in Lancashire, by Dr. "William Roberts, and 

 another in Norfolk, by Dr. Beale. The general range of 

 the disease is within the limits 30° south and 30° north 

 latitude. Probably, what is known as elephantiasis 

 arabum — which must not be confoimded with elephantiasis 

 grsecorum or leprosy — is also to be attributed to the 

 presence of the same parasite. 



This parasite has only been known to science in recent 

 years. In 1866, Dr. Wucherer foimd several specimens at 

 Bahia, in the urine of a patient suffering from chyluria, 

 and two years later. Dr. Salisbury described, under the name 

 of Trichina ci/stini, some worms which he had found in the 

 urine of an insane person, and which now appear to have 

 been nothing else than Filnria snniiuinis. About the same 

 time. Dr. Lewis of Calcutta, not knowing of Wucherer's 

 discovery, called attention to observations that had been 

 made by him of a similar character, and in 1872 he 

 published that he had found nine specimens of the same 

 kind of hannatozoon in some blood which he had extracted 

 from the finger of a Hindoo who was suffering fi'om 

 elephantiasis arabum. Dr. Lewis had sent specimens of 

 his first case to Dr. Parkes and Mr. Busk in this country, 

 and they had diagnosed them as belonging to the Filaridffi ; 

 and afterwards he gave to them the name of Fihrria 

 sanf/uinis hoiiiinia. These, however, were all cases of the 

 discovery of the immatiu'e or embryonic worms. The 

 mature worm was discovered in 1876 by Dr. Bancroft at 

 Brisbane, and in the early part of the next year by Dr. 

 Lewis in India. Dr. Cobbold then gave to it the name of 

 Filariii Buncni/'fi, a name which has been rightly discarded 

 for the prior one of Dr. Lewis. Since then the mature 

 worm has been seen bvDrs.Los Santos and Aranjo in Brazil, 

 and by Dr. Manson in China. It is interesting to note 

 that the mature worm is only known to exist in the 

 lymphatics of its host, and that the immature or embryonic 

 worm is found not only in the chyle but also in the blood. 

 The female worm is about 3 inches in length and about 

 jJ „th of an inch across, of an opalescent colour, thread-like, 

 and appearing "like a delicate thread of catgut, animated 

 and wriggling." The head is club-shaped, the mouth 

 circular and destitute of papilla-, and the body devoid of 

 transverse striations. Except an alimentary canal, which 

 runs a straight and narrow course from head to tail, the 

 body is made up almost entirely of the reproductive organs. 

 The animal is viviparous, and is contimuilli/ giving birth to 

 fully-formed embryos. These embryos are of about the 

 yV*!! to y'fjth of an inch in length, and about the KsVr.tli or 

 TTs'tic of an inch in diameter. They are thread-like (see 

 Fig. 1), and enclosed in a sheath, like a baby in a caid. 

 When examined under the microscope in a drop of blood 

 they exhibit quick eel-like movements, lashing the red 



