The mosquito then repairs to water to deposit her ova. Many of the embryo nematodes are digested, but some are expelled with the excreta, or having penetrated into and completed their development in the thoracic and abdominal tissues of the mosquito, bore through its body wall and escape as free nematodes. Probably they are swal lowed by the human subject with the water, but of this step we have BO accurate knowledge as yet. On re-entering the human body the parasite reaches sexual maturity and locates in the lymphatic sys tem. Here probably conjunction of the sexes takes place and filarial embryos are produced in vast numbers.
Dr. Manson's researches were confirmed by Dr. Lewis, of Calcutta, who found four out of eight mosquitoes captured at random in one of the servant's houses contained specimens of embryos. Dr. Araugo, of Bahia, verified the presence of the embryos in mosquitoes who had fed upon the blood of a French priest afflicted with filaria. Drs. Bancroft, of Brisbane, and Sonsino, of Cairo, corroborate these facts.
The parent worm produces either living embryos or aborts and emits these in an immature stage in the shape of semi-spherical ova.
The former are one seventy-fifth of an inch long and their breadth is about the diameter of a red blood corpuscle. Their size enables the free embryos to penetrate the walls of the capillaries, but the un hatched ova in which the embryos lie coiled up are of larger diame ter, and their size renders their escape from the finer capillaries impossible. They are, therefore, arrested in the first lymphatic gland which may be reached. Blockage of the gland ensues, more filari accumulate behind the obstruction, and a localized lymphatic congestion results ; the process spreads, with consequent dilatation and varicosity of the lymph vessels which drain into that gland.
The greater the number of glands thus affected the wider will be the area of dilated lymph channels, the highest expression of dam age due to obstruction being found when the thoracic duct is im peded, as in Mackenzie's case. Thus, it is only needed for a prolific female, aborting or miscarrying from some as yet inexplicable cause, to expel her ova in numbers into the lymphatic circulation, to pro duce plugging more or less complete of the lymphatic glands through a limited or an extended area according to the location of the worm (Mastin).
The blockage of the lymphatic trunks may take place in any part of the body, hence many lymphatic diseases, which were formerly considered separate and distinct, are now established as being due to filarial obstruction.
Dr. Bancroft enumerates the following conditions among others as being probably associated with filariEe : Chylocele, varicocele, elastic tumors in the axilla and groin (hel minthiasis elastica), lymph vesicles bursting on the scrotum and ab domen, skin diseases (craw-craw), elephantiasis of the scrotum, abscess of the scrotum.
In a remarkable case published by Sir William Roberts in 1868 a coagulable chylo-lymphous discharge escaped from open vesicles which had formed over the surface of the abdomen. After death it was found that the cutis vera and the subcutaneous tissue were trav ersed by short lymphatic channels or lacunpe, from the width of a crow-quill to that of a hair—apparently a vast intercommunicating lymphatic mesh.
The immediate cause for the appearance of chyle in the urine is the direct communication between the varicosed and dilated lacteal channels and seine part of the urinary tract, combined with intermit tent or chronic obstruction to the thoracic duct or a large branch of the same.
This communication may take place through the lymphatics of the bladder with the interior of that viscus, as was proved by Havel burg in the case a woman who had lived in Brazil for fourteen years. It is reported that the urethra of this patient was so dilated by the passage of chylous clots that a catheter was easily inserted into the ureter, and, being retained there for two hours, clear urine flowed through it. This showed that the entrance of chyle was due to the direct lesion in the bladder. She had also a small patch of elephantiasis in the integument of the epigastric region. At the post-mortem a large lymphatic sac was found on the left side extending from the true pelvis to the kidney. This was full of white blood-streaked fluid. The left side of the upper part of the blad der was quite imbedded in the recesses of the sac referred to, and when opened the bladder was found to be perforated in this situation.
But in two cases which I had the opportunity of examining, the orifice of communication was situated in the upper part of the urinary tract. The first, which is known as Dr. Mackenzie's case, I dis sected in a somewhat novel manner, after a plan I had followed in working with Professor Braune, of Leipzig, upon the valves of minute venous channels of the abdominal walls.* I mention this here as it is, in my opinion, the only sure method of dissecting such flimsy structures as dilated lymphatic sacs, and believe with Sir W. Rob erts that the failure to discover communications is due to the want of deliberate care and of some method of counteracting the collapse of the thin-walled sacs after death.