250 NORMAL PARTURITION. 



/"Longitudinal 



Ph 



I'Dorso-sacral. 



I Right Dorso-ilio-sacral. 

 /'Natural Positions -' Left Dorso-ilio-sacral. 

 I Right Dorsoilial. 



Anterior J VLeft Dorso-ilial. 



I r Right Dorso-supra-cotyloid. 



^Abnormal Positions^ Left Dorso-supra-cotyloid. 



[ Dorso pubic. 



?Lumbo-sacral. 



I Right Lumbo-ilio-sacral. 

 'Natural Positions -; Left Lumbo-ilio-sacral. 

 Right Lumbo-ilial. 



/'Natural Positions -; J 



^PosteriorX vLeft Lumbo-ilial. 



I i Right Lumbo-supra-cotylold. 



lAbnormal Positions- Left Lumbo-supra-cotyloid. 

 I Lumbo-pubic. 

 [ Right Cephalo-ilial. 

 [ Dorso-lu7nhar — Abnormal Positions - Left Cephalo-ilial. 

 .Transversei ^ Cephalo sacral. 



I r Right Cephalo-ilial. 



yStcrno-abdominal — Abnormal Positions - Left Cephalo-ilial. 



\ Cephalo-sacral. 



The longitudinal presentations, with natural positions of the trunk of 

 the foetus, do not necessarily imply an easy birth, as, independently 

 of disproportion between the dimensions of the passage and those of the 

 foetus, there may be a misdirection of the head or Hrabs, which would 

 constitute dystokial presentations. 



SECTION III.— MECHANISM OF PARTURITION. 



Under normal conditions, it may be said that the pelvis itself does 

 not offer any obstacle to the passage of the fa3tus, and that it is the soft 

 parts alone which oppose its exit. 



Of the different presentations enumerated, the anterior — in which the 

 fore feet, head, and chest present simultaneously-^is the only one we 

 may designate as " natural," especially with the larger animals and 

 primiparae. 



Fromage de Feugre was the first to point this out, though Eainard 

 was of opinion that the posterior presentation should also be looked 

 upon as normal ; while Desplas gave three natural positions — head and 

 fore limbs, head only, and hind limbs only ; and Delwart gives four 

 normal positions. But experience abundantly proves that the first we 

 have described is that which alone merits the designation, as it is the 

 one in which birth can take place without artificial aid. It is true that 

 birth is possible when the Foal or the Calf presents posteriorly at the 

 pelvic inlet ; but this is a rare presentation, and under the most 

 auspicious circumstances it is much less favourable, and more difficult 

 for the mother, while it is very often death to the young animal (espe- 

 cially in the Mare). In the majority of cases, without assistance ex- 

 pulsion proceeds no further than the hocks, and the foetus dies ; and 

 even sometimes with assistance much force is necessary to deliver. 

 Whereas, in the anterior presentation, the cases are exceptional (and 

 these chiefly in primiparae) in which even slight traction is necessary. 



We will follow Saint-Cja- in first studying the mechanism of parturi- 

 tion in this presentation, in which, of the eight positions pertaining to 

 it, the vertebrosacral is by far the most frequent and favourable. This 

 we will now notice. 



