THE LARGE INTESTINE OF THE PIG 489 



or the point b is the actual apex. If a is selected, the adhesions 

 of the mesentery and of the adjacent coils may be torn apart so 

 that the spiral may be unwound as shown in figure 16. It 

 would then consist of two parallel limbs, which, in this speci- 

 men, make 3| revolutions. If b is taken as the apex, the coil 

 may be unwound as shown in figure 17. Beginning at the valve 

 of the colon as before, there are now only three revolutions. 

 It is evident, however, that the unwinding shown in figure 16 

 is natural, and that the other is an 'artificial' dissection, for 

 the adhesions yield more readily in the former and there is less 

 tearing of the mesentery. Moreover, at the base of the spiral, 

 the proximal and distal limbs of the coil early become adherent 

 to one another and to the body-wall, establishing a fixed point. 

 The basal hmbs retain this position in figure 16, but have been 

 separated in figure 17, so that, the former is clearly the correct 

 picture, and the true apex is at a. 



Additional revolutions may take place without changing the 

 apical pattern. If half a turn is added to the coil shown in 

 figures 15 and 16, the bend a will be carried up between y and z 

 toward b, and the conditions shown in figures 18 and 19 will 

 result. In figure 19 the bend ap, which before unwinding the 

 coil appears to correspond with b in figure 15, is clearly the 

 true apex. 



The number of revolutions actually produced varies, and 

 small fractions, generally neglected, appear quite as often as 

 whole or half turns. Hunter, in the passage cited, speaks of 

 'five spiral turns,' evidently referring to the five tiers shown in 

 figure 14. In this specimen, however, beginning at the valve of 

 the colon, there are but four revolutions, and this appears to be 

 the normal number. Bonnet's statement that there are 3^ can 

 be applied to this specimen only by regarding b as the apex 

 instead of a. 



The length of the spiral portion of the colon in the young 

 adult (fig. 14) is 2.6 meters. The distance from the cohc valve 

 to the apex is 1.4 meters, or 53 per cent of the total length. 

 Thus the apex is finally located just beyond the middle of that 

 part of the colon which forms the spiral. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 20, NO. 3 



