Parasites: A Treatise on the Entozoa of Man and Animals: Including Some Account of the EctozoaCobbold, T. Spencer (Thomas Spencer)
Science
Parasites: A Treatise on the Entozoa of Man and Animals: Including Some Account of the Ectozoa
Cobbold, T. Spencer (Thomas Spencer)
Helminths; Parasites
these researches had quite as much to do with the measles or Cysticerci
of beef as they had with those of the hog, if not more. Naturally but
few foreign investigators can have had access to the work in which
Lewis’s experiments were originally recorded, and to which, therefore,
I must call their attention. Thus, Dr Tommasi has fallen into the error
of supposing that the investigations of Lewis were made in England. It
is of very little moment where the experiments were carried on, but
Tommasi’s statement (appendix, loc. cit., p. 161), wherein he says that
Pellizzari’s experiments, in which he himself took part (_ai quali
io stesso ho assistito_), are even more complete than those made in
England by Dr Lewis, and in Germany by Dr Küchenmeister, cannot be
allowed to pass unchallenged. If Tommasi had enjoyed the opportunity of
consulting Lewis’s original memoir, he would not have underestimated our
countryman’s labors. The memoir by Lewis is singularly complete, and
well-nigh exhausts all the facts that can have any interest in relation
to the question of public health. Towards the close of his essay he
expressly states, as the result of investigation--“(1) That exposure
to a temperature of 120° Fahr. for five minutes will not destroy life
in Cysticerci, but that they may continue to manifest indications of
life for at least two or three days after such exposure; (2) that
exposure to a temperature of 125° Fahr. for five minutes does not kill
them; but (3) after being subjected to a temperature of 130° Fahr. for
five minutes, they may be considered to have perished. After exposure
to this and higher temperatures, in no instance have I been able (he
adds) to satisfy myself that the slightest movements took place in
their substance when examined even under a high power. At least, it
may be confidently asserted that, after exposure for five minutes to
a temperature of 135° to 140° Fahr., life in these parasites may be
considered as absolutely extinct” (p. 139). Thus the statements of Lewis
and Pellizzari were in perfect accord; and seeing that their conclusions
were alike the result of very careful and independent inquiry, it seemed
as if the question at issue was finally solved. These investigations
made it perfectly clear that Cysticerci of all kinds, whether found in
veal, beef, or pork, could not retain their vitality when exposed to a
temperature of 60° Centigrade, or, in other words, 140° Fahr.
The rather severe strictures made on Perroncito’s earlier experiments
induced the Turin professor to go over the subject more carefully, when
he obtained excellent results. He finally ascertained that Cysticerci
perished at a temperature below 50° C. (122° Fahr.). In May, 1877, Dr
Perroncito furnished me with an account of his researches. With the
exception of a few verbal alterations, for which I am responsible,
Perroncito wrote as follows:
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