On the 2nd of November I found my solitary strongyle larva alive, but its movements, though active, were by no means so active as on the previous day. No fresh structural changes had occurred.
At noon on the 3rd the larva at first lay almost motionless in the now thick and ropy saliva; nevertheless, on applying a thin glass cover its movements became tolerably vigorous. During its quiescent state I succeeded in getting a good view of the caudal rays and other imperfectly developed organs, of which I retain figures.
Having now satisfied myself that other new conditions were necessary to enable the larva to arrive at sexual maturity, I sought to transfer it to a glass tube filled with fresh saliva. This transfer was a matter of difficulty. After passing the thick ropy saliva into the tube, I examined the slide and found that the larva was gone. I concluded it was in the tube, which, in order to keep the contents warm, I subsequently carried about concealed in my under-clothing during the day and placed in my bed during the night. This increase of temperature, however, caused decomposition of the saliva; so when next day I diligently sought for my experimental nematode it was nowhere to be found. Thus terminated my observations on the first set of embryos, which had enjoyed their temporary sojourn in the intestinal tract of the earth-worm, and which had certainly afterwards undergone a series of marked structural and morphological changes, accompanied with ecdysis.
The weather had now been for several days exceedingly cold, but on the 4th a favorable change set in, which led me to hope that I might be able to verify the facts above recorded. Accordingly, as a new point of departure, I re-examined the fine mould, and at once found my embryos in a high state of activity. The mould, however, appearing too moist for the earth-worms, I permitted further evaporation before closing the jar with a glass cover. Four days subsequently I examined the intestinal contents of two of the earth-worms. In one of these, an inch in length, no parasite of any kind could be detected; but in the other, which was beyond three inches in length, there were numerous Opalinæ besides several strongyle embryos, the latter presenting characters not visibly in advance of those still living in the mould. All of them were motionless, as if they had not got over the shock produced by previous cold. Moreover, the weather had again become cold, and thus, when I again inspected my experimental embryos living in the jar, I also found them motionless, so different from their behaviour on the 4th. However, since a further result with the earth-worm embryos appeared possible, I placed some of the fæcal matter, already ascertained to contain a few of them, on the fronds of a thoroughly moist and dew-covered Asplenium bulbiferum. This plant was in a fern-pan which had the advantage of considerable fire-warmth during the day. When, however, on the 15th of November, I examined the fæcal earth removed from several of the pinnules, I failed to find any of the embryos. Possibly they had wandered, for the entire frond was covered with dew-drops, which was not the case with the fern that I had previously experimented on with such satisfactory results. At all events, whether they had wandered or had perished, their apparent absence in no way affects my previous record; and the more so since only a few had been observed in the fæcal matter. The smallness of the number found in the earth-worm was also readily accounted for. Thus, when at 1.30 p.m. on the 15th I made a diligent search for embryos in several grains of the fine mould, not a single young strongyle could be detected. Possibly the frost of the previous night had killed them. The earth-worms were still alive and in good condition.
In conclusion, I may observe that every experimenter with helminths is well aware how unfavorable the winter season is for this kind of research. If a repetition of this inquiry in the spring or summer should confirm these results, it will prove a clear and substantial addition to our knowledge of the development of the strongyles. Meanwhile, I think that the data above given render it highly probable that the larvæ of the hoose-producing strongyle (S. micrurus) are passively transferred to the bodies of setigerous annelids, which are thus called upon to act as intermediate hosts. If this be so, it is further certain that important structural changes with ecdysis follow after their escape from the earth-worms or other annelids, moisture, dew, or water being essential to the penultimate stage of growth. Final passive transference, either with fresh fodder from swampy grounds, or, it may be, from pond water, ultimately enables them to acquire their definite sexual form, size, and other adult characteristics.
According to Mégnin it is not the Strongylus filaria, but a hitherto unknown and totally distinct species (Strongylus minutissimus) which occasions pneumonia in Algerian sheep. In England the parasitic bronchitis affecting sheep is generally called the “lamb disease.” This is unfortunate, because many other parasites prove destructive to lambs. One of the most injurious species is Strongylus contortus, infesting the true stomach, whilst S. hypostomus, occupying the small intestines, is almost equally obnoxious to the ovine bearer. By Leuckart and others this last-named worm is retained in Dujardin’s genus Dochmius, in which genus another species occurs (D. cernuus). This worm is quite distinct, but not readily distinguishable by the naked eye alone. It occasionally occupies the upper part of the colon, as well as the lower end of the small intestine. A rarer intestinal worm in lambs is the Strongylus filicollis. Several other strongyles infest the ox (S. radiatus, S. inflatus, S. gigas), goat (S. venulosus), and stag (S. ventricosus).
As showing the extraordinary prevalence and destructiveness of entozoa in certain countries, I will adduce an instance in which my opinion was requested and given some five years since. My informant stated the case somewhat in the following manner:—On a farm in New South Wales, and lying about 200 miles to the north-west of Sydney, on the Trafalgar tributary of the Macquarie river, out of a flock of about 8000 sheep no less than 1200 have perished. In many instances post-mortem examinations were made, worms appearing in all cases to be the cause of death. There were four kinds of parasites present. The most numerous were red and white, “marked like a barber’s pole.” These occurred chiefly in the fourth stomach and commencement of the duodenum, but some were found throughout the entire length of the small intestine. A second set comprised small black worms, resembling needles, scattered only in the lumen of the intestines. The third set were tapeworms, each being several fathoms in length. The fourth set was made up of white threadworms, individually measuring two inches in length. These occupied the bronchial tubes, and were characterised by my informant as “the most deadly of all.” Without the aid of specimens I at once recognised these brief diagnostic characters as severally referring to Strongylus contortus, Dochmius hypostomus, Tænia expansa, and Strongylus filaria.
What the inquirer desired at my hands was “full information respecting the general principles to be carried out in view of the prevention of this parasitic disease, regard being had to the difficulty of finding any food but pasture, to the number of animals to be treated, and to the not unfavorable circumstance that the run is divided by fencing to a great extent.” I was also requested to explain the best modes of treatment, being at the same time informed that turpentine drenchings had already been employed with only “partially effective” results. I was also expected to give numerous and varied formulæ, to be tried in succession, supposing the first should fail. Of course, it should have been known that I neither prescribe medicines nor accept fees in respect of animal patients; but, as in this instance my opinion was permitted to assume the form of a “written scientific report,” I was pleased to have an opportunity of commenting freely and fully on the significance of the facts submitted. My advice took the form of a long report, which might here be usefully given in extenso were it not somewhat of the nature of a private and privileged communication. I have no doubt that the stockowner would be pleased that I should utilise his remarkable “case” for the benefit of agriculturists and others; but it is for him to publish the “opinion” as it stands, should he think fit to do so.
Practical men, on reading the few foregoing particulars, will perceive that one of the principal obstacles to success in cases of this kind lies in the circumstance that artificial food can only be procured with difficulty. Where the source of the disease is associated with the pasture-supply, any treatment, however effectual for a time, can only be followed by partially satisfactory results.
The destructive powers of any one of the above-mentioned parasites being sufficient to produce a fatal lamb-disease, it is clear that when two or more of these particular species attack their victim in considerable numbers, the ovine-bearer has little chance of recovery. The intestinal strongyles, by means of their oral armature, behaving as veritable leeches, will, if not expelled in good time, produce a rapidly fatal anæmia, precisely in the same way as the human Anchylostomum of the tropics.