136 



PELVIS. 



nml the tuberosities of the isthia are near each 

 other so as to present a small opening at the 

 interior outlet. Scemmerring remarks that 

 the obturator foramen is more elliptical in 

 the infant than in the adult. The depth 

 and general appearance of the true pelvis 

 is smaller than is proportionate to the iliac 

 wings ; and it is of nearly equal breadth 

 throughout. 



The parallelism of the lateral, as well as of 

 the anterior and posterior pelvic walls is, I 

 think, sufficiently marked and general to be 

 considered as a characteristic of the con- 

 formation of the infant pelvis, as we shall find 

 it to be of that of most of the lower animals, 

 giving to it a square-sidedness which is well 

 seen in the adjoining figure. 



Fig. 8.5. 



crease, than to dimmish, the pelvi-vertebral 

 angle. 



Pelvis of the Child at birth. 



The sacrum and coccyx in the child at 

 birth are much less curved, vertically, than 

 they afterwards become, which causes the 

 posterior wall to be longer than is propor- 

 tionate. The coccyx, indeed, in many in- 

 stances I have seen, was almost vertical. 

 The sacro-vertebral angle is consequently 

 much less marked than in the adult. Doubt- 

 less, muscular action, increasing as the de- 

 velopment of the bones progresses, has a 

 great effect in producing the diminution of 

 the sacro-vertebral angle backwards in after 

 life. 



It is commonly stated by anatomists, that 

 the infant pelvis is more obliquely placed on 

 the spinal column than the adult pelvis. The 

 inclination of the superior plane in the child 

 has been placed by the brothers Weber at an 

 angle of 15-i'GG with the transverse vertical 

 plane. This is somewhat less than the in- 

 clination in the male, according to the same 

 observers, viz. 155. 



The following table is the result of the 

 measurements of the pelvic angles of five 

 infants, made to ascertain the correctness of 

 this statement. The angles were carefully 

 taken, with much precaution against any ab- 

 normal displacement, so readily occurring in 

 the pliant structures of the infant, by makinjr 

 an antero-posterior vertical section of the 

 pelvis and whole spinal column with the whole 

 of the soft parts attached, and in such a 

 manner as would have tended rather to in- 



It will be remarked that the greatest dif- 

 ference from the adult is observable in the 

 sacro-vertebral angle, which is from 10 to 15 

 greater than the average female adult, and 

 from 23 to 28 greater than the average male 

 adult. 



I should here state, also, that the results of 

 my own measurements of the angle of the 

 superior pelvic plane in adult male subjects, 

 have given somewhat less angles than that 

 stated by Weber. 



According to Cruveilhier, a horizontal line, 

 from the upper border of the pubis, meets 

 the posterior wall much lower in the infant 

 than in the adult, though the point at which 

 he places it in the adult, viz., a little below 

 the base of the sacrum, is much too high in 

 the natural position of the pelvis, as will be 

 seen by inspection of the diagram (fig. 81.). 

 In all the infant pelves 1 have just given, 

 the tip of the coccyx reached as low as the 

 lower border of the symphysis pubis ; both 

 these points exactly coinciding with a line 

 drawn perpendicular to the transverse verti- 

 cal plane. This may, perhaps, be attributed 

 to the greater flatness of the sacro-coccygeal 

 wall in the infant, extending it further down- 

 ward. In No. 5. the male child at full term, 

 the angle of inclination of the pubic symphyxis 

 to the transverse vertical plane was only 

 25, but in the last female child it was, 40, 

 both being less than the mean adult angle, 50, 

 before given, and showing, like the sacro- 

 vertebral angle, a greater tendency to parallel- 

 ism with the spine, as in the inferior animals, 

 an analogy which is also seen in the elongated 

 conjugate diameter. 



Resulting from this tardy development of 

 the pelvis, the bladder and greatest portion 

 of the rectum, in the child at birth, are con- 

 tained almost entirely in the abdominal cavity, 

 on a level with the ilia or false pelvis, and 

 only descend gradually afterward into their 

 adult position with the slow development of 

 the pelvic bones, assuming their permanent 

 position about the period of puberty, a cir- 

 cumstance very necessary to be borne in 

 mind in operations on these viscera in chil- 

 dren below that age. Hence one cause of the 

 greater prominence of the belly in children 

 from the additional number of its visceral 

 contents. 



