144 



KNOWLEDGE 



[Atjgust 1, 1891. 



Fig. 1. — Embryos of FHaria saiii/iiin 



corpuscles in all directions. The number of them Ln the 

 blood of a person affected with the disease of which they 

 are the concomitants must be enormous, and Dr. Stephen 



Mackenzie has 

 reason to believe 

 that the blood of 

 a patient who 

 came imder his 

 care contained 

 from thirty-six to 

 forty millions. 

 The eggs are 

 about jTioth by 

 yiyth of an inch 

 in length. A 

 complete specimen of the male form has not yet been 

 obtained, but Dr. Lew-is found a broken specimen half an 

 inch in length and y^th of an inch across. It was 

 thinner and firmer in texture than the female, and showed 

 a great tendency to coil. 



The following measurements of a female specimen will 

 serve to distinguish this species fi-om any other Filarian : — 



Of an Inch. MM. 

 Oral aperture to end of oesophagus ... JL or '45 



Diameter of oral aperture ... ... ... -3^^ „ '008 



Width of neck ... ... ... ... _>_ ^^ -045 



„ about J inch from anterior end ... ^|. „ -162 

 „ where packed with ova and embiyos you m '"'^ 

 Comparing its characters wath those of Truhimi Kpirnlu 

 and the embryo of the Guinea worm (Filaria nudincnsis), 

 the only two human parasites with which it may be con- 

 foimded, we have — 



?; in. 



J, in. I 1 to 46 



TaU. 



Blunt 

 Acutely 

 pointed 

 Acutely 

 poiuted 



Trichina spiralis 



Filai*ia medinensis 



[Embryo.] 

 Filaria san^iuis homiuis . 

 [Embryo. 1 



The greatest peculiarity of these parasites is their 

 diurnal variation. If the blood of an affected person be 

 examined between 6 a.m. and 6 p.m. none, or only a few, 

 can be detected, while at 9 p.m. they are more abundant, 

 and at or about midnight the blood is swarming with 

 thcrn. About 3 a.m. their numbers begin to appreciably 

 decline, and at 6 a.m. no trace of them can be found. 

 This periodicity was first observed by Dr. Manson, and 

 has since been confirmed by Drs. Myers, Stephen 

 Mackenzie and Lloyd Jones. What the reason of this is, 

 has not yet been satisfactorily determined. Dr. Manson 

 supposes that as day dawns they migrate to the blood- 

 vessels of distant organs, like the lungs, where they cannot 

 be easily detected; while Myers, reasoning on his observa- 

 tion that they become more languid and lethargic as 

 morning approaches, thinks that they die out, and that a 

 new swarm of embryos is produced by the females for the 

 forthcoming night. However, the observation of Myers 

 has not been confirmed, and it must be pointed out, as 

 against his theory, that the parturition of the parent is 

 not intermittent but continuous, and the enormous 

 numbers in the blood can scarcely be considered as a 

 single brood, even on the assumption that more than one 

 fertile female is present in the system of the affected 

 person. However, what determines their presence in the 

 blood during the night-time has been clearly proved to be 

 the resting condition of their human host. In a case 

 which was imported from India to this coimtry, and which 

 came under the observation of Dr. Stephen Mackenzie, 

 the patient changed his habits of life, and remained out of 

 bed during the night, and slept during the day for a period 



of three weeks. The result was that the Filarial were not 

 found at all in the patient's blood during the night, but 

 existed in immense quantities during the day-time. Dr. 

 Manson has since confirmed this, and has also shown that 

 if the general sleep of eight hours' duration be broken into 

 two periods of four hours each, their numbers are sensibly 

 diminished. Dr. Mackenzie has also shown that if the 

 patient is awake and on the move during a thick and dark 

 London fog, no specimens can be found in the blood. 



Considering that they are chiefly embryos which are 

 found in the human body, this periodicity is interesting in 

 another relation. It has been shown by Dr. Manson that 

 they have an intermediate host, and that intermediate host 

 is a ndcturmil sjiecies of mosquito, a species which has not 

 been determined, but which can be recognised in the 

 localities in which diseases from Filaria sanyuinix occur by 

 its dark brown colour and the absence of any markings on 

 its abdomen, thorax, or legs.* Dr. Manson persuaded a 

 Chinaman, who had embroyos of these Filariie in his blood, 

 to sleep in an outhouse which was infested with this special 

 species of mosquito. He in the morning killed these 

 mosquitoB, which of course had been feeding upon the man, 

 and found numbers of the embryos in their stomachs, and 

 by a series of observations has shown that although some 

 of them are digested yet others pierce the thorax of the 

 mosquito and go through a series of changes in the 

 surrounding tissues, which lead to a perfect fitness on the 

 part of the parasite for an independent existence. This 

 takes place in about four or five days. About the sixth or 

 seventh day the mosquito, having laid her eggs on the 

 surface of some pond, dies, her body becomes decomposed, 

 and the Filariie escape into the water, which after being 

 drunk by some unsuspecting person they perforate the 

 walls of his stomach and intestines and find their next 

 resting-place in his lymphatics, just as the Trichina spiralis 

 does in the muscles and the liver-fluke in the bile-ducts. 

 The cycle now commences again ; the adult female gives 

 continuous birth to embryos in the lymphatics, and these, 

 being no larger than the red corpuscles, make their way by 

 the thoracic duct into the general blood stream, and so on. 



It must not be supposed that persons who have Filarise 

 in their blood are always afl'ected with symptoms of 

 chyluria or elephantiasis arabum. Indeed it has been 

 shown conclusively by Drs. Hall, Paterson, and others, 

 that such is not the case, and that they may occur in the 

 blood without gi\'ing rise to any external symptoms of 

 their presence. But these two diseases are essentially due 

 to obstructions in the flow of lymph throughout the body. 

 Dr. Manson and several others have observed that some- 

 times ova instead of embryos escape from the vagina of the 

 female, and it seems to be due to this abortive development 

 that the diseases in question are produced ; for these 

 ova, not having the propulsive movements — the eel-like 

 wrigglings before described — of the embryos cannot get 

 through the narrow channels of the lymphatic glands, 

 and so by their numbers dam back the lymph stream 

 and stop its flow. They, in fact, act like, what is 

 called in pathology, an embolus. As says Dr. Manson 

 in his paper, which was read before the Pathological 

 Society in 1880, " There will be a complete stoppage of the 

 lymph m this particular vessel, as far back as the first 

 anastomozing lymphatic. Along this the current will now 

 pass, carrying with it other ova ; these, in their turn, will 



* The proboscis of this mosquito seems to be adapted in some inex- 

 plicable way for the purpose of extracting the embryos from the 

 blood. The embryos become entangled in, or attracted to it, and a 

 drop of blood taken from the proboscis of the mosquito contains a 

 larger niunber than a di-op of blood obtained from the person who b^s 

 been bitten, 



