The width of the cleft varies as much as the extent, and is a matter of great importance prognostically, as the broader clefts are much more difficult to close. The direction or slope of the segments of the bony palate also differs considerably, in some instances being more or less horizontal and following the normal curve; in others one or both of the segments is much more nearly vertical, a condition which is not at all unsatisfactory, for, as will be explained hereafter, the more horizontal the palatal processes, the more difficult is it to gain satisfactory closure by operation ([p. 65]).
The frequency of the occurrence of harelip and cleft palate cannot accurately be ascertained, inasmuch as statistics are not readily to be found. In the ‘St. Thomas’s Hospital Reports’ the number of malformations of the children born is noted in some of the years. Thus the aggregate number of living children born in their maternity department in the years 1875, 1877-1880, and 1883 was 10,653, and of this number there was only one case of harelip, with two cases of cleft palate, and three of the combined deformity, i. e. about one case in every 1800 infants born; but if the silence of the reports for subsequent years means absence of deformity, then this proportion may be much too great.
On the Continent some old records are obtainable. Thus, according to Grenser, of 14,466 infants born living at the Maternity at Dresden from 1816 to 1864 there were sixteen cases of simple harelip, and nine with fissures of the palate. Credé states that amongst 2044 infants examined at birth, only one case of simple harelip was observed, and one of complete division of the hard and soft palate.
Occurrence in Animals.
These conditions obtain not only in the human subject, but also in animals, though not so commonly.
Thus Sutton figures a right-sided harelip in a slink calf, and mentions a specimen of a harelip in a lamb in the museum of the Odontological Society; and in our museum at King’s College there is a specimen of a right-sided harelip in a kitten with a cleft alveolus, but the palate is intact.
Cleft palate occurs more frequently in animals, particularly in those born in a state of captivity. Thus it appears that from statistics taken ten years ago 99 per cent. of the lion cubs born in the London Zoological Gardens had cleft palates, indicating that either the food-supply of these animals was not all that was requisite for perfect development, or that enforced confinement has a deleterious effect upon the multiplication of the species. It is a curious fact that in the Dublin Zoological Gardens the deformity was rarely noticed amongst the lion cubs, and the reason for this was supposed to be the supply of such food that the mother could eat both flesh and bone. Since the same practice has been followed in London, viz. giving the lions twice a week a young goat which they can eat, bones and all, the proportion of cleft palates in the young subsequently born has become considerably diminished.