364 Tlie Lung Parasites of Cattle and Sheep, 
most remarkable, if it be not the most common, of all the lung- 
worms ; and it is certainly the source of grave disease. The 
pathological appearances produced by its presence have been 
fully described by Alois Koch ; and the worms themselves have 
been studied, not only by the Vienna helminthologist, but also 
in this country by Professors Brown and Axe, by the late 
Dr. Crisp, by the writer, and likewise long ago by Messrs. 
Sandie and Padley. On account of its hair-like form and 
excessive transparency, the coiled-up worm is readily over- 
looked. When unrolled, the full-grown parasite measures from 
five-sixths of an inch to a trifle more than one inch, the sexes 
being nearly equal in length. However, the thickness of the 
body of the female does not exceed the of an inch in 
diameter. 
Life-history of the Worms. — As it is almost certain that 
in their main features all the strongyloid lung-worms of cattle 
and sheep pass through similar or analogous stages of growth, 
development, and metamorphosis, attended with and consequent 
upon both active and passive migrations, accompanied by 
a change of hosts, it is sufficiently obvious that a thorough 
knowledge of the phenomena exhibited by any one of the 
species cannot fail to serve as a clue towards a correct under- 
standing of the life-history of all the others. Not improbably, 
however, the Pseudalius, or little gordian worm, pursues a 
somewhat different course of development. Certainly, indeed, 
the notion put forward by the late Dr. Crisp, to the effect that 
the sheep's gordius " is the early condition of both the filaria 
and the strongylus,^^ is entirely erroneous. Although an honest 
and laborious investigator, the late Dr. Crisp's views about the 
entozoa, generally speaking, were untenable, whilst his last 
memoir on the so-called gordian worm is marred by palpable 
misunderstandings and by false interpretations as to the 
significance of the facts observed. 
The Embryo. — If a full-grown female lung-worm from the 
calf be examined with a low magnifying lens, its body ^ will 
be found to be crowded with eggs, of which a large proportion 
contain fully-formed young in the embryo state. I have 
reckoned that a large and well-developed worm contains at 
least 100,000 of such embryos ; but Mr. Beulah, a microscopist 
and practical agriculturist, estimates that the lung-worm of the 
sheep carries as many as 300,000 embryos. If we reckon in 
this calculation the im[)erfectly-deve]oped embryos, Mr. Beulah's 
enumeration is probably much below the mark. Anyhow,- 
these figures do not fairly represent the full germ and embryo- 
producing power of one female worm ; because, as long as the 
parent worm continues to live, she produces fresh germs and 
