Crystallographic Studies on the Eggs of Various Human Parasites

I. Observation with Polarization Microscope

Abstract

Recently, the use of polarization microscopes has become gradually more common in the domains of biology too. In 1928, Runnström¹⁰⁾observed the fertilization membrane of the egg of sea-urchin with a polarization microscope and has first pointed out its double refraction. More recently, Schmidt, ¹¹⁾ Inoue and Dan¹²⁾ have observed similar phenomena, Schmidt giving a minute description of the double refraction shown in the egg-shells of ascaris and pointing out that this double refraction comes from chitin in the shell. As detailed in the above, I have observed under a polarization microscope that the shells of eggs of various parasites show double refraction and have been informed that these shells have crystalline structure. Hereunder, I will subject to further discussion the above findings of the eggs of various parasites under a polarization microscope and their crystallographical properties and characteristics.
The shells of the eggs of ascaris show the highest stability, with their thick shells of crystalline structure showing strong double refraction and ellipsoid form. Upon swelling and separating the outermost layer by Ida's method, it was found that the next layer was the thickest and showed the highest degree of double refraction, greatly contributing to the stability of the shell. The second layer was found to have radially arranged crystalline structure, indicating its presumably high crystallizing aptness as nucleus. In general, it is of course necessary that an adequately powerful supporting basis is present, if a crystal is to grow to a size. From such a view-point it is needless to emphasize that a fertilized egg of ascaris with very high stability and with a thick layer of crystalline substance in its shell offers an ideal nucleus in crystal formation. The presence of an albuminoid layer is a characteristic peculiar to an egg of ascaris not shared by an egg of any other parasite. Its uneven surface of large superficial area, its high cohesiveness and easy stainability are important factors in performing its duty of protecting the egg. They also conform with its aim at multiplying the chance of infection by adhesion to external objects. Its propensity to invite pigmentation and under definite circumstances to receive precipitation of crystals has been proven in the above described experiment. In this case, the albuminoid membrane is preserved to play the part of the skeleton of the forming crystals. The crystallographic properties ascertained in the above study are clearly of the nature that will, if a groundwork favoring a growth of crystals exists in the medium, lead to a growth of crystals too.
The unfertilized eggs of ascaris, however, have thin shells with only low double refraction, showing a perceptible difference from the fertilized eggs and indicating a probable frailty. It may be supposed that a partici-pation of calcium and other inorganic components has a considerable influence in forming the fertilization membrane.¹³⁾ Such properties of an unfertilized egg probably make it worse adapted to form a nucleus of a bile stone than a fertilized egg, even if laid in the bile duct and the bile had acquired the predisposition facilitating the stone formation. Of course, the difference in the pictures of an unfertilized and a fertilized eggs under a polarization microscope offers a means for differentiating the two.
The eggs of hookworm and of trichostrongylus orientalis have only thin shells of low double refraction indicating a frail structure like the unfertilized eggs of ascaris. This property seems to he of service, when the early-grown youngs hatch out of the shells. Generally speaking, these parasites may have some chances to invade the biliary duct, and even if some of them enter the duct, they are not so apt to cause its stasis.