486 CETACEA. 



of the true uterine cavity. The sides of the base of the horn are thrown into longi- 

 tudinal mucous folds of no great strength. 



Mucous surface of uterus of gravid female. — The extreme thinness and seeming 

 smoothness of the walls of the left horn are what at first strike the ohseryer. The 

 left horn does not average more than 0-06 inch, and in this, as already remarked 

 (page 395), it is in strong contrast to Orcella, hut the wall of the common cavity of 

 the uterus is twice as thick. The greatest thickness occurs in the two septa of 

 the horns, in which it attains to 0-18 inch, hut in the mesial septum it is some- 

 what less. 



The mucous surface is marked by certain coarser and smoother areas, the latter 

 predominating in the left horn and the former on the common cavity, and in the 

 right horn. Both are of a spongy texture, and radiate from the Eallopian openings 

 of these cavities along their long axes as in Orcella (antea, p. 395) and correspond, 

 the first to the folds and the second to the intervening spaces between the folds of the 

 virgin womb. It must not, however, be supposed that the distribution of these 

 rugose areas of the left horn is at all prominent or well defined, but the course of 

 the rugae is, to a certain degree, discernible. Eour can be observed radiating inter- 

 ruptedly towards the uterine orifice of the horn, but they are so little raised above 

 the general surface of the mucous membrane that I hesitate to estimate to what 

 extent they project beyond it. They occur as linear bands of variable diameter. 

 The best marked runs from the Eallopian orifice along the upper third of the dorsal 

 wall of the horn to the mesial septum, and another, much shorter and more indistinct, 

 and separated from the former by an interval of about an inch and a quarter, has only 

 a very limited distribution from its origin. Two other coarsely spongy bands run 

 from the Eallopian opening along either side of the attached border of the horn, and 

 extend to the origin of the left septum. In the right horn there are five of these 

 folds radiating from the Fallopian orifice. They are slightly annulated folds of the 

 mucous membrane, and they can be traced more or less continuously to the uterine 

 orifice of the horn. At the beginning of then course they are raised above the 

 surrounding mucous surface, even to a quarter of an inch, and are thus the most 

 strongly pronounced folds in this uterus. The common cavity of the uterus does 

 not present the fine spongy texture of the smoother parts of the horn, but is rough 

 throughout its extent, the equivalents of the primitive folds of the virgin womb 

 being more obliterated than in the right horn. Six, however, are discernible, 

 radiating upwards from the os uteri internum as in Orcella, but they are little raised 

 above the general sm'face. The septa are thrown into well-marked folds on both 

 their surfaces, with the single exception of the left side of the mesial septum, which 

 is not rugose. The folds run parallel to the free margins of the septa and 

 anastomose more or less with each other. 



The mucous membrane of the uterus between the coarser folds. — The areas 

 which I have compared to the spaces that intervene between the folds of the virgin 

 womb, exhibit a tendency, more or less, to have the fibres of their fine spongy texture 

 arranged in lines transverse to the direction of the coarse folds, iJut beyond these, 



