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Show 1894.] CURYATURE OE THE SPINE IN PISHES. 99 the second of the two furnished by Prof. Sutton. The entire column consists of 48 vertebrae, and its most noteworthy feature is a single flexion involving the 30th to the 35th of the series. These are so modified (fig. 4 a) as to form an arch, of which the 33rd (c. 33) is the keystone. The ventral compression of the 33rd vertebra of this specimen is more marked than that of any similarly modified vertebra with which I am. familiar; and in accordance with this and the corresponding adaptive shelving of the anterior faces of the 34th and 35th, the succeeding vertebrae must in life have been disposed at a sharp angle to those in front of them. It is characteristic of the specimens which I have thus far described that where sinuosity occurs synostosis is uneffected, but inasmuch as in the example now under consideration vertebrae nos. 31 and 32 (cf. fig.) are partially united, that so far bridges over the gap between the sinuous and compressed types. This union is seen to be the outcome of an extension of the right base of the 31st haemal arch (a.h. 31), that structure, as it were, having welded together the two vertebrae. In correlation with this there have arisen a series of displacements involving only the right side, rendering it at first sight apparent that the 35th and 36th haemal arches are double. This is in reality not so, for detailed analysis shows that the right half of the 32nd haemal arch had become shifted back and confluent with the body of the 33rd vertebra, while the corresponding halves of the 33rd and 34th arches had become similarly shifted and co-ossified with the vertebrae (34th and 35th) next in order of succession behind. The two halves of the 36th haemal had, in sympathy, but insignificantly united beneath the haemal canal, and the right half of the 35th had entirely disappeared. The arches of the remaining vertebrae of this specimen are normal; but those of the distorted region present, in addition to the features already described, an irregular lateral disposition, those of the 31st and 32nd especially being so modified as to conform in end view to the limbs of an S-shaped curve. There can be little doubt that the synostoses, compressions, and sinuations afore described are, as Hyrtl surmised for the first-named, congenital in origin. As remarked at the outset (ante, p. 95), it is generally the custom to regard the causes producing congenital curvature of the spine as unknown. This may be so for lateral curvature, but concerning the vertical variety herein dealt with a consideration arises. The facts which I have recorded appear to m e to point towards the conclusion that divergent as the conditions of sinuation and compression with or without co-ossification appear, they are in reality the opposite effects of one and the same disturbing influence; and, indeed, the indication of a sinuous arrangement in the compressed type (fig. 6) suggests that they are perhaps even more closely related. In both there results an approximation of the opposite spinal extremities, and, in relation to the vertebrae of each individually disturbed series, of the opposite 7* |