Positions of the Fetus 533 



of the mother is divided into quadrants which represent the sac- 

 rum, pubis and right and left iha. Toward either of these areas the 

 dorsum of the fetus ma\- be directed, whether presenting by the 

 anterior or posterior end. 



It does not follow that the dorsum of a longitudinall}- present- 

 ing fetus is always directed toward the center of one of the four 

 areas mentioned, but there may be every possible degree of vari- 

 ation, the four cardinal points of the pelvic girdle serving as a 

 basis for the designation of the intermediary or "oblique" 

 positions, or simple variations, by which any one position may 

 gradually merge into the next. In the longitudinal presenta- 

 tion, the fetus tends to spontaneously assume that position in 

 which its dorsum corresponds to the sacrum of the mother. 

 This we designate as the dorso-sacral position. (See Figs. 87 

 and 88). 



It is pre-eminently the normal position. While it is the- 

 oretically possible for birth to occur, without assistance, in 

 other positions of the longitudinal presentations, such has but 

 rarely been observed. In the anterior presentation and dorso- 

 sacral position, the disposition of the three extremities, the head 

 and two anterior limbs, determines the practicability of the fetus 

 being expelled without assistance. In animals wath long and 

 rigid limbs and a small head, such as the large herbivora, the 

 normal relationship is for the two anterior limbs to be fully ex- 

 tended, with the soles of the feet presenting downward, while 

 upon these rest the head and neck with the nose somewhat less 

 advanced than the two anterior feet. In the mare the nose rests 

 in the vicinity of the fetlocks ; in the cow the no.se is somewhat 

 nearer to the hoofs. Any deviation in the relationship of these 

 extremities at once causes difficulty in the pa.ssing of the fetus 

 through the birth canal and brings about more or less .serious 

 dystokia. 



If the fetus revolves upon its long axis to the extent of a 

 quadrant of a circle, either to the right or the left, the dorsum of 

 the fetus corresponds to the right or left ilium respectiveh^ and 

 causes the right or left dor.so-ilial position, a position of the fetus 

 which renders spontaneous birth difficult in all cases, and usually 

 impossible without obstetric aid. 



Should the revolution of the fetus upon its long axis continue 

 a quadrant further, the dorsum of the fetus corresponds to the 



