358 



head, there would then be formed two organs instead of one, 

 which would always be contiguous and apposite. 



Suppose this segmentation to divide the entire germ, and 

 at a very early period, there would result a double monster, 

 as, for instance, the Siamese twins ; or, suppose the fissuration 

 to occur at a later period, and of only a portion of the germ, 

 there would follow supernumerary parts, such as fingers, legs, &c. 



I have now before n.e a duck with two heads, but which is 

 sino-le otherwise throughout. It is only necessary to consider for 

 a moment the embryological conditions of the oviparous verte- 

 brates, to perceive that this duplicity could have occurred only in 

 a single-yolked egg. 



I would maintain, therefore, in this connection, that in terato- 

 logy, monsters by duplicity of organs, must be considered due to 

 a more or less complete segmentation of a single germ or egg, 

 instead of a fusion of two germs. 



Let me now refer to our own case of hermaphroditism in re- 

 lation to this point. How, it will be asked, can the anatomical 

 conditions of the organs in this case be reconciled with the hypo- 

 thesis, that there was here a segmentation of this portion of the 

 germ ? The answer to this question leads me to refer to a point 

 in Anatomy, which has been but recently appreciated. I refer to 

 the Vesicula prostalica, or Uterus masculinus of Weher. This is 

 an anatomical feature which, although perceived by Morgagni 

 and others of the older anatomists, was truly discovered by Weher, 

 for he first recognized its true morphological import. It is found 

 only in Mammalia; and in man consists of a small, flask-shaped 

 vesicle, with a rounded blind end, and a narrow neck, directed 

 downwards, placed on the posterior wall of the urethra, under the 

 Veru montanum, and covered by the prostate. It is usually from 

 three to six lines in length, and two lines or so in breadth. The 

 vasa deferentia open beside it, one on each side, though not 

 directly into its cavity, as is the case with the hare (Lepus.) * 



* For references to the Vesicula prostatica, see 

 Morgagni^ Adversaria Anat. IV. Animad. 3. 



Albinus, Annotat. Acad. IV. Tab. III. fig. 3. p. 25. "'■ 



SchUcJiting, Syphilidos Mnemosyn. Criticum. Amsterd. 1646, fig. 4. 

 Severinus, Zootomia democrita^a, p. 329. 



