IRREGULARITIES OF THE DENTAL APPARATUS. 



725 



b. Diminution. 



Irregularities from diminution in the number of the teeth are perhaps less 

 common than the preceding ; they must not be confounded with the phenomena of 

 a tardy eruption, with those of arrest of development, in which the teeth remain 

 enclosed in their alveoli without ever piercing the gums, or, finally, with those 

 of fractures and of extraction, which are quite often met in old horses. __They can 

 only result, in their true sense, from an arrest of development of the dental 

 follicles; they entail no evil consequences, and 

 may exist in the incisors, the canines, and the 

 molars. 



1st. Incisors. Rudolphi 1 has noted the 

 absence of one of these teeth in the horse, but 

 gives no specific description. 



M. Megnin 2 has observed the absence of a 

 left pincer in the adult horse. 



In our experience, we have noted, in a 

 horse fifteen years of age, the absence of the left 

 intermediate and corner. 



Absence of the corners, of which we pos- 

 sess some specimens (Fig. 313), has been cited. 



In June, 1887, a horse was presented to us 

 in which the four corners and the four tusks 

 were wanting. 



Relative to the diminution of the number 

 of incisors of the first dentition, M. Bizard 3 

 has succeeded in obtaining the jaws of a colt 

 twenty-eight months of age, in which the infe- 

 rior pincer of the left side did not exist. 



More recently our colleagues, Messrs. 

 Laine and Joly, 4 have mentioned the absence 

 of the inferior pincers of the first and second 



dentition in a subject which they have been able to observe during a sufficient 

 length of time. 



M. Ch. Morot 5 has also presented to the Central Society of Veterinary 

 Medicine two analogous cases, but involving the superior corners. Besides, he 

 has demonstrated that this numerical reduction of the teeth is in obedience to 

 the laws of heredity. He has also shown that the non-existence of the milk- 

 teeth means a suppression of the corresponding permanent teeth ; at other times, 

 on the contrary, the eruption of the latter was not in the least hindered. 



2d. Canines. The absence of the superior canines, either on one side 

 or on both, is more frequent than that of the inferior. But it is very excep- 



FIG. 313. Absence of the inferior 

 corners. 



1 Rudolphi, cit6 par Isidore Geoffroy Saint-Hilaire, in Histoire g6n6rale et particuliere des 

 anomalies de 1'organisation, t. i. p. 658. 



2 Megnin, cite par le Dr. Magitot, loc. cit, p. 103, et suiv. 



3 Bizard, note communiquee. 



4 Lain6 et Joly, note communiquee, 1887. 



5 Ch. Morot, in Bulletin de la Societ< centrale de medecine veterinaire, Seance du 23 

 Novembre, 1882. 



