The Microscope in Silkworm Cultivation
Monthly Microscopal Journal, May 1, 1869, VII. p. 304-309.
The report which M. Pasteur recently published, and which he was so good as to send me, indicates the great progress which has been made in this direction. Supported by a great number of bets, expressed with an order and clearness which an experienced observer can alone obtain, M. Pasteur has established it as an axiom that the healthy egg of caterpillars, which are themselves healthy, and have been carefully cultivated, should not only furnish a good product, but also healthy caterpillars, which in their turn should deposit healthy eggs. He thus proclaimed, with the authority of his word, the utility of the microscope, which utility I myself and my fellow-countrymen have contended for on all occasions when experiments or observations enabled us to do so.
Indeed, for several years some of my friends have had marvellous crops of cocoons by selecting eggs free from corpuscles which I had selected for them after very careful investigation. With a microscopic examination, limited to the eggs, we make only a half experiment. This method is imperfect, and the incomplete success resulting from its employment may be attributed (excepting certain bad processes of culture) to examination for corpuscles in the eggs only, for every healthy egg does not necessarily produce a healthy moth. These facts are evidenced by the feet that eggs attacked in the proportion of 4 per cent if proceeding from one of our families of moths, or 8 or 9 per cent, if from one of the Japanese races, give very mediocre results. In fact, the corpuscles which 1 have often insisted on, are the appreciable characters of the disease; but the eggs may be attacked by the original disease without having these microscopical features. In examining the eggs of a corpuscular female, in which they were disposed in chaplets in the ovaries, all the eggs were not found charged with corpuscles.
In order, then, to make a definitive experiment to guarantee the healthiness of the eggs, thexe is nothing like examining the moths before or after they have deposited their ova, in order that we may reject all those eggs proceeding from tainted parents. This mode, the most rational, although the most difficult of execution, which M. Pasteur has suggested, and which I believe to he alone capable of regenerating our races of worms, was attempted last year at Milan with complete success. The results I published in my letter to the 'Perseveranza;' but I ask permission now to describe in detail some of the results which the experiments of 1868 in Lombardy enabled me to formulate.
In the month of June, 1868, I received from Zara a chambrée of cocoons of the ancient Italian race, cultivated on the Dalmatian coast, not far from the shores of the Adriatic. These cocoons, about one kilogramme, contained three chrysalides alive. Some of these chrysalides, which I soon examined, and which were not yet perfect, exhibited no trace of the corpuscles. It was then that the idea occurred to me of applying M. Pasteur's method to the eggs obtained from healthy moths grown with every care . . .
My friends the Marquis Crivelli and M. Bellotti undertook this experiment. The moths, when hatched out, had a most deceptive appearance, and, when examined by these gentlemen, were found to be free from corpuscles; here there was a perfectly healthy egg, the product of healthy parents, which gave promise, not only of a large produce in cocoons, but even of a healthy crop of moths and of eggs for the culture of the year 1869.
M. Crivelli selected Inverigo, in Brianza, to "bring up" these eggs, in order to surround them with all the necessary care. He divided the eggs into three portions; one of these parcels was given to a peasant in the village, another was reared in his own garden, and the third was sent to a distant locality.
It is necessary to state that the mode of "education" adopted by the Marquis was an extremely careful one; general hygienic conditions being carefully attended to, and the locality, which had some time ago been used as a hospital for cholera patients, having been fumigated with chloride of lime. Within a radius of 500 metres, no other silkworms were cultivated. Moreover, the locality abounded in mulberry-trees — this fact being of importance, — for had the leaves been imported from other localities, they might have been tainted with corpuscles of diseased caterpillars.
 The cultivation of the three batches proceeded excellently, as on the estate of Inverigo, where the Marquis raised 210 ounces of eggs, of which no more than two per cent, were diseased. From these 210 ounces he obtained 10,176 kilogrammes of cocoons, a mean of 48 kilos. to the ounce. The three batches of eggs from Zara did still better; for they produced a maximum of cocoons equal to 62 kilos, per ounce.
As may be imagined, the Marquis set apart for the next year the eggs from the last-mentioned quality, and he set to work with ardour, and with great hopes of excellent results. But all his exertions were not followed by equal success.
The examination of the chrysalides responded exactly to what might have been predicted; that is to say, that all three batches were equally healthy. The microscopic examination of the moths, however, gave quite a different result. Those which had been reared in the village and those in the Marquis's garden were diseased; but those which had been sent to a distance and which were brought up in the isolated house were perfectly healthy. Not one of these last presented any corpuscles, neither in leaving the cocoon nor in depositing ova, nor in decay, nor after death.
Here there is a decisive result; for the eggs were the same and the education of the three batches was alike, save in certain circumstances, on which it is important to insist. All had the same abundance of air, all were equally chambrées, all had excellent food. The peculiar circumstances relate only to the conditions of contagion—to the transport of corpuscles. In fact, the healthy moths were those which had been reared under circumstances of isolation, in places previously disinfected, and where the worms had been fed with leaves equally isolated.
Here there is what is essential to obtain certain results. To the ordinary precautions of "education," conducted with all possible attention as to temperature, aeration, and abundance of food, it is necessary to add isolation of the chambers by a cordon of at least 500 metres radius, and healthy eggs, deposited by healthy moths, cultivated with particular care in isolated localities, disinfected with chlorine, and having a certain "precocity," (1) in order to obtain isolation.
The experiment has not been made on a very small scale; for M. Crivelli has been able to obtain 480 ounces of these perfect eggs; and it was in this harvest that he obtained the maximum of 62 kilos, of cocoons to the ounce.
M. Bellotti, to whom I had given the other portion of the healthy eggs, and who raised them at Varese with his usual skill  and care, also obtained a large produce in cocoons; but the moths which came from them contained corpuscles. He had not isolated his chambers.
This, then, is why in some localities, as the Apennines, in Dalmatia, and in Istria they have always good crops of cocoons and sound eggs. The localities are much more isolated, than ours are. The hatching-grounds are at the summit of hills and in conditions most favourable to avoid contagion.
See what has occurred this year in Istria. For several years I have myself examined the eggs cultivated by MM. Villanova de Farra, not far from Trieste (they rear some thousands of ounces), and they have so far recognized the importance of my predictions, that they wished this year to carry out experiments on the subject. I therefore sent to them M. Gaddi, who has been accustomed to this sort of microscopic work in my laboratory. He set out with his microscope to Istria, and visited several localities. In the course of his travels he examined fifty-four different lots of cocoons, commencing with the examination of the chrysalides, in order to reject those which were diseased.
Out of fifty-four different batches, only five (Nos. 8, 11, 17, 35, and 49) exhibited 10 per cent, of corpuscles, and therefore these presented favourable chances of obtaining healthy moths. It is necessary to state that even in the same batch of chrysalides there might be different proportions of healthy and diseased specimens, accordong to the degree of maturity. The chrysalides just formed partook of the condition of the worm; these, which were many days older, partook more of the condition of the moth. In one case (No. 36) the chrysalides just formed showed only 4 per cent, of infected specimens; but, after some days, they presented as much as 70 per cent, of corpusculated specimens. Thus we may lay down the proposition that the chrysalides just formed exhibit the disease much in the same degree as the corresponding egg; those, however, which are near their transformation present the disease in a much more marked degree. Of the several lots examined, three only gave indications of healthy produce. The results of the examinations of these is given in the following Table:—
 In lot 35 of 1268 moths 345 were of the best character. Thirty-eight were less fine specimens, and 885 were of couples separated by the "cellular method." It is with these excellent ova that MM. Levi await the harvest of the ensuing year. M. Crivelli has been equally fortunate with the lot isolated in the manner before referred to.
It is difficult to establish a proportion between the disease as it appears in the egg and as it afterwards exhibits itself in the moths, because of the different periods at which the examination is made. If the examination be made too early, it may discover 0 per cent, in the chrysalides; 30, 50, or 60 per cent, in the moths; and, again, 0 per cent, in the eggs proceeding from these. These proportions have been found by M. Crivelli The corpuscles are propagated with an incredible rapidity, and sometimes in the last moments of the life of the chrysalides, when the eggs are already formed—a feet which explains why a great number of corpusculated moths may present eggs which contain no corpuscles.
In the experiments in "cellular" breeding it has been found that the. males hardly ever propagate the disease to the females. In the tables prepared by M. Crivelli, where the male was diseased and the female healthy, the eggs also were invariably healthy. Is it that the spermatozoa enter the ovum by a channel which does not allow the passage of the corpuscles? Irrom observations which I have conducted, I deduce that the disease in the ova is to that of the moths as 1 to 10. Here are some examples of this:—
From the foregoing remarks and general experience, I draw the following conclusions:—
Letter from Signor Cornalia to M. Pasteur, read to the French Academy, and published in the 'Comptes Rendus,' (2) LXVIII, No. 11, 1869.
Cornalia, Emilio (Badassare Maria)
was an Italian naturalist, zoologist and mineralogist. He was born
21 July 1824 in Milan in Milan and died in
the same city on 8 June 1882 . He was conservator from 1851 to 1866, and director from 1866 till
his death, of the Milan Museum of Natural History, and was interested in all
areas of biological science.
He was one of the group of leading scientists instrumental in founding La Società Entomologica Italiana, the Italian Entomological Society. He was the author of important works of applied entomology, such as Monografia del bombice del gelso published in 1856, published together with Prof. Paolo Panceri, (1833-77), the latter more often working on marine organisms than Cornalia [Anseropoda pancerii (Gasco, 1870), Lampea pancerina (Chun, 1979), Microcotyle pancerii Sonsino, 1891, Sciaenocotyle panceri (Sonsino,1891)]. Among his articles on marine organisms is a description of a sardine parasite (crustacean)."Sulla Taphrobia pilchardi, nuovo genere di crostacei parassiti" in Soc. Ital. Sci. Nat., Atti, 18, 1875, 2. fasc., p. 197–200. Cornalia was also part of a scientific expedition to the upper Nile valley in 1873.
Il s’intéresse à presque tous les domaines de l’histoire naturelle. En 1856, il étudie les corpuscules caractéristiques des vers à soie atteints de pébrine. Ces corpuscules avaient été découverts en 1849 par Guérin-Méneville, mais Cornalia ayant montré nettement leurs liens avec la pébrine, ils resteront connus sous le nom de «corpuscules de Cornalia».
This page compliments of Marisa Ciceran
Created: Sunday, August 10,
2008; Last updated:
Wednesday, October 10, 2012