Doncaster Microscopical Society
The twelfth ordinary meeting of the above society was held on Wednesday evening, the 18th inst., the Rev. W. R. Weston (vice-president) in the chair.
Thirteen members were present
In the absence of Mr. J. B. Withington, two papers were read on the parasites infecting pork, one by Dr. J. Mitchell Wilson on Trichina spiralis, the other by Mr. W. Walker on Cysticercus cellulosae.
As a large amount of interest throughout this and other countries has recently been manifested in the parasitical disease affecting pork, which are capable of being communicated to man, the following points, alluded to by Dr. Wilson and Mr. Walker, may be of interest to general readers.
The Trichina spiralis belongs to the group of round worms, and is most frequently observed enclosed in a cell or cyst, curled up in a spiral shape. These Cysts, which are found only among the muscles of the meat, are scarcely visible to the naked eye.
Under the microscope, the worm in its free state measures in the female one-eighth of an inch in length, and the male only one-eighteenth of an inch. The young in each female has been estimated at from 10.000 to 15,000.
Within two or three weeks after obtaining an entrance into the stomach, say from imperfectly cooked pork, these enormous numbers of young are born, and at once begin their wanderings. They burrow along the muscular tissues, becoming encysted, and it is during this stage that the violent muscular pains are experienced, which are a prominent sign of the disease in man.
Dr. Cobbold estimated that in one person, who had eaten a known quantity of pork infected with trichinae, there would be at least 42,000,000 parasites, Some of the epidemics which have occurred in Germany have caused a mortality of less than 2 per cent of the persons attacked, while in 18765 an outbreak in one town attacked 350 persons, of whom 100 died. Numerous inquiries have been made as to the prevalence of this parasite in pork in different countries.
1n 1866, out of 1,400 hogs examined at Chicago, 28 were found infected, or 1 in 50, the number of worms in each cubic inch varying from 48 up to 18,000. In France the disease Trichiniasis has always been rare. In Germany the disease has been much reduced since the introduction pf compulsory microscopical examination.
Professor Gamgee states that the Yorkshire and Berkshire pigs are generally free from worms. He adds, we disregard the most common precautions to protect ourselves against disease, by allowing piggeries where all kinds of garbage, charged with worms or their eggs, are devoured by swine. Dr, Wilson had carefully examined eighteen specimens of pork obtained from shops in different parts of this district, but none of these were any trichinae found. Specimens were, however, shown, obtained by a friend at a distance, from a piece of ham infected with the parasites, and other prepared slides exhibited infected muscle both from man and the pig.
It is said that a temperature of 160 deg. Fahr. Kills the free trichinae but the encapsulated worms are able to resist a greater degree of heat, and are not destroyed by the usual methods of smoking, pickling, or roasting the meat. If the interior of a piece of meat, roasted or boiled, retains much of the blood and colour of uncooked meat, the temperature has not been higher than 130 deg. Fahr.
These facts ought to lead us to observe the advice of the medical officers to the Local Government Board, who say that any sample of meat thought to contain the parasite, ought not on any account to be eaten, no matter how it is cooked, and that the only means of avoiding disease in man from the dangers arising from trichinae in meat from pigs is by very though and efficient cooking, which means generally cooking it one-half as much again as the ordinary rule.
At the conclusion of Dr. Wilson’s paper, Mr. William Walker, M.R.C.S. gave a short account of Cysticercus cellulosae, the larval form of the tapeworm, Taenia solium.
The presence of these parasites constitutes that disease in pig commonly known as the measles. Under the microscope they appear as small, egg-shaped bodies lying between the muscle fibres. Although the larvae are found in other animals besides the pig, the mature tape worm exists only in man. The head of the Cysticercus is of globular form, furnished with four suckers round the margin, and fourteen or more hooklets in the centre. When the egg or germ of the tape worm is swallowed by an animal it is hatched in the stomach, and afterwards forces its way into the various tissues of the body, where, like the trichinae, it becomes encapsulated, and remains dormant, forming the Cysticercus. When flash thus infested, is swallowed by man, the Cysticercus is developed into the fully-formed tape worm.
In connection with this parasite, there is the advantage that when present it cannot easily be overlooked, as the meat infected with it has a very characteristic appearance. Should there be any doubt, the discovery of the hooklets under the microscope would at once dispel it.
The reading of the paper was followed by an interesting discussion in which the chairman, the authors, the Rev. W. Smith, and Messrs. Burman, Kirk, Stiles, and Tindall took part. The meeting terminated with a vote of thanks to Dr. J. Mitchell Wilson and Mr. Walker.
[Doncaster, Nottingham * Lincoln Gazette, May 27, 1881]