GENERAL ARTICLES. 199

REFERENCES.

(I) Ransom, B. H.: The Life-History of Habronema Musc::e (Carter), a Parasite of the Horse transmitted by the House-fly. "Bullet. 1 6 3 of Bureau of An. Ind.," 3rd April 1913. '

(2) Railliet: Contribution it l'etude de I' "esponja" ou plaies d'ete des equides du Bresil, par J. Descazeaux. "Recueil de Med. Vet.," Tome XC!., Nos. 19-20, January-September 1915, p. 468 . • (3) Johnson, T. Harvey: Notes on some Entozoa. "Proc. Roy. Soc. Queensland," Vol. XXIV., 1912, pp. 63-91.

(4) Lewis, J. c.: Equine Granuloma in the Northern Territory of Aus­tralia. "Jr. Camp. Path. and Thera.," Vol. XXVII., No. I, 31st March 1914, p. r.

ON A CASE OF HOLOACARDIUS ACEPHALUS IN A BIRD.

By PHILIP BRUCE WHITE, B.Sc., Assistant Pathologist, Trinity College, Dublin.

THE specimen which forms the subject of this paper exemplifies one of the extreme forms of acardius acephalus which fall under the head of omphalosites. These latter constitute a group of composite monsters in which the two individual parts-an antosite and a parasite - are in vascular communication z!id a common placental region, or, in the case of non-placental animals, through the vasculosa of the common yolk sac.

With this prelude I proceed to the description of my case. The specimen, obtained in a dried condition, was hatched from

the same egg as a normal duckling. Externally the specimen consisted of very little more than a pair of hind limbs, which in contrast with the remainder of the animal-if it is possible to term it such-showed a wonderful degree of development. The feet were scaled, the legs and the rudiment of the body were clad in feathers. The limbs had suffered considerable rotations which were not easy to analyse, and at one end of the body were shrivelled remains of the yolk sac.

After immersion in water an attempt at dissection was made, but though some of the soft organs could be identified their details could not be made out; what remained of the body muscles had undergone fatty changes. The skeletal parts were much modified and reduced; they are figured in the accompanying sketch.

The axial skeleton was entirely absent. The main bones-the limbs excluded-were those of the pelvic girdle. A small lamina of semi-cartilaginous bone represented the sternum, while a few minute rods were apparently ribs.

As shown in fig. 2, the pelvic rudiments consisted of two pairs of elements. Of these, two bones, presumably morphologically dorsal and the representatives of the ilia, were compressed rods fused into an irregular spongy mass at their acetabular ends, crossing at an acute angle. Below these and parallel to them Were a second pair of fairly cylindrical bones also fused to the acetabular mass. The ends of these four bones distal to the acetabulum were free, and, to

200 GENERAL ARTICLES.

judge from the insertion of the omphalic remains between them and the supposed sternum, were directed posteriorally. With this inter­pretation of their orientation the first-mentioned pair must represent the posterior wings of the ilia and the lower pair the ischia. The arrangement of the feathers also supports this conclusion.

The acetabula were very imperfectly formed, there being only rough depressions for the femora.

From the nature of the case the specimen may be classified as a holoacardius acephalus, var. peracephalus.

The parasite described exhibits a great similarity to one in the Heidelburg collection figured by Schwabe,! who writes concerning it: "An dem Nabel des wohlausgebildeten HUhnchens hangt an einem Strang, der durch die Reste der Eihaute und des Dottersacks gebildet ist, ein befederte Kbrperteil, der dem Steiszende eines

z.

HUhnchens enspricht und zwei wohlausgebildete hintere extremitaten tragte."

The genesis of acardii, as these monsters have been rather inaccur­ately termed,2 has been explained in more than one way, and has formed the subject of some controversy.

Though the case I have described does not contribute to our knowledge of the teratogeny of acardii, a few words on the subject may be a propos.

The factkns may be divided into two main groups :-(1) Those who hold that the twins were originally of equal rank,

one subsequently undergoing malformation as a result of certain relations to its congener. Ahlfeld supposes two embryos to develop in one ovum, but that one develops more rapidly than the other. Vascular connections are established which in some way encompass the degeneration of the heart of the less advanced embryo, and therefore an only partial nutrition of its body. In the case of birds

1 "Die l\Iorphologis der Missbildungen des l\Ienschen und der Tiere,"Il:. Teil, Kap. X., s.159. 2 In the lower grades of the malformation distinct remains of a heart may be present.

GENERAL ARTI(:LES. 201

anastomoses of the vessels of the vasculosa would presumably be the cause of the malformation, while in the case of mammals the earlier formed allantois interpolating itself between the second allantois and the chorion would furnish anastomoses with the former.

(2) Those who, with Darest, Marchand, and Rabaud, attribute the inequality of the twins to a primary inefficiency of the parasite so incompatible with life that any development is only possible when a secondary connection, respiratory 2nd nutritive, is established between the two unequal twins.

That is to say: Does the inequality of the antosite and parasite arise as a result of the relations of the two twin embryos, or is it determined independently of these relations?

As already stated, the case in hand does not assist in any way in deciding between these two theories, but it is interesting to note how such anatomical fragments, enabled to nourish themselves and respire, can carry their" self differentiation" to such a pitch in the apparent absence of co-ordinating centres and of many organs which under normal circumstances are. essential.

JOHNE'S DISEASE.

THE REACTIONS OF ANIMALS TO "JOHNIN."

By Sir JOHN M'FADYEAN, M.B., B.Sc., LL.D., A. L. SHEATHER, B.SC., M.R.C.V.S., and J. T. EDWARDS, B.Sc., M.R.C.V.S.

(From the Research Institute in Animal Pathology, Royal Veterinary College, London.)

(Continuedfrom page I7I.)

INTRACUTANEOUS TESTS OF CATTLE.

SERIES 1.

TESTS OF ANIMALS EXPERIMENTALLY INFECTED WITH JOHNE's DISEASE.

On the 10th August 1911 Calves I, 2, and 3 were inoculated intravenously with an emulsion of J ohne bacilli. They were sub­sequently subjected to two intracutaneous tests with concentrated avian tuberculin, dose icc., the results of which were as follows:-

Calf I.

26th March 1912. There was a just appreciable thickening of the anal fold from the ninth to the eighteenth hour.

4th October 1912. The anal fold reached a maximum of between two and three times the normal at the sixth and fifteenth hours only. A t other times up to the seventy-fifth hour the thickening was only just appreciable.