142 THE STRUCTURE OF MAN 
have, as a rule, more than five, and sometimes as many as eight. 
The Edentata possess from six to eleven (Orycteropus has eleven, 
Dasypus nine, Bradypus and Manis seven, Myrmecophaga six), 
and the Primates from one to three. 
At a late embryonic period three olfactory ridges are often 
present in Man, inasmuch as between the superior and inferior 
a third projects into the lumen of the nose (cf. Fig. 87). 
This last, when present, is more or less distinct at birth, but 
it becomes reduced later, the superior ethmo-turbinal, as a 
rule, growing over it like a cover. With this superior ethmo- 
turbinal, which must be considered as primary, the rudiment 
of a fourth is found (cf. Fig.); but this is further differentiated 
only in exceptional cases. We thus have at least four ethmo- 
turbinals represented in the developing human nose, with three 
olfactory meatuses; and this arrangement recalls those Mammals in 
which there are four corresponding ridges present in the adult. 
[Concerning variation of 
the olfactory meatuses of 
the human adult, on recent 
examination of 152 indi- 
viduals, the dominant con- 
dition—presence of three— 
was observed in 56 per 
cent; four were noted in 
41 per cent, and five in 
‘1:3 per cent. In _ three 
_ ;_, stances (7.e. approximately 
in 2 per cent) only two were 
found, the superior turbi- 
nated bone being absent; 
and in one of these “there 
Fro, $8.—Saarma, SHOMON THROvGH 2% was si horizontal plate of 
Human Heap. cartilage projecting into the 
I, II, IIT, the three olfactory ridges ; sn’., frontal nasal fossa from the septum 
sinus ; sv”., sphenoidal sinus ; 0s., opening of ’ 2 p ‘ 
Eustachian tube ; bc., entrance to the mouth; on a level with the inferior 
lg., tongue ; v.t., atlas vertebra; v.i., axis : 2 
aes , , turbinated bone. ] 
When it is further re- 
membered that the maxillary, frontal, and sphenoidal sinuses 
(sn’., sn”., Fig. 88) are also lined by olfactory mucous membrane, 
* [Made under the auspices of the Collective Investigation Committee of the 
Anatomical Society of Great Britain and Ireland. See Jour. Anat. and Phys., 
vol, xxviii. p. 73.] 
