Dt Herdman on the " Olfactory TubeTcle!' 265 



form, but in all is completely closed. In these the greater 

 diameter is always placed transversely. 



The second type is more normal. The shape of the tubercle 

 is still very variable, but horns and an aperture are always 

 present, though the position and size of the latter are by no 

 means constant. The form of the tubercle is usually lozenge 

 shaped or rudely triangular, the posterior end is pointed, and 

 in the commonest form the aperture is at the anterior end 

 but directed to one side, most frequently the left ; the horns are 

 both turned in, but are unequal, the right one being generally 

 much larger than the left, and coiled spirally. The simplest 

 form of this type is a tubercle which forms about three- 

 fourths of a circle, the posterior end being rounded, the horns 

 bent towards each other, and the aperture wide and placed 

 rather to the left of the anterior end. The first complication 

 is caused by the horns being turned more sharply inwards, so 

 as to diminish the size of the aperture ; the shape has also 

 varied a little, the posterior end having become more an- 

 gular. This leads to the typical form in which the posterior 

 end is pointed, the aperture at the left side of the anterior 

 end and the horns both turned in, one, however (the right), 

 being much larger than the other. An exact sinistral 

 variety of this has occurred once or twice, in which the 

 aperture was at the right side, and the left horn was the 

 larger of the two (Fig. 14). 



Fig. 14. 



A very marked variation (Fig. 15) still remains to be men- 

 tioned. The shape of the tubercle was triangular, but the 

 base was posterior and the angle anterior, while the aperture 

 was at the left extremity of the base. The left, or, in this case, 

 posterior horn was rudimentary, while the right or anterior one 

 was enormously developed, turned inwards quite to the centre 

 of the tubercle. This variety is evidently derived from the 

 typical form by the disproportionate development of the two 

 sides, the right horn from its enormous size occupying all the 



