THE SENSE ORGANS 141 
THE OLFACTORY ORGAN 
The Number and Structure of the Olfactory Fiudges 
and the Turbinals 
Following Broca and Turner, we may divide Mammals, accord- 
ing to the development of their olfactory apparatus, with especial 
reference to its cerebral portion [“rhinencephalon,’ “lobe lm- 
bique ”] into series, viz. : 
[i. Osmatic series, turbinals present and usually five in 
number. | 
(a) Macrosmatic [organs of smell largely developed], (most 
Mammals, eg. Edentata, Ungulata, Carnivora, Rodentia, Mar- 
supiaha, and Lemuroidea). 
(6) Microsmatic [olfactory apparatus relatively feeble] (Pinni- 
pedia, © Whalebone - Whales, 
Apes, Man, and Monotre- 
mata). 
[11. Anosmatic series, or- 
gans of smell, apparently 
absent in the adult |—(Dol- 
phins and Toothed - Whales 
generally, although many of 
these require further investi- Fic. Sf LATE VIEW OF THE NASAL 
gation with regard to this CHAMBER OF A HuMAN EMBRYO. 
point). Li iii thes threes. oltactory, ridees: ; 
; +, supernumerary ridge which occurs in 
The first point to be the embryo; x., tip of the nose; pi., 
established is the primitive hard palate ; cr., base of the skull; o0s., 
: ostium of the Eustachian tube. 
number of the olfactory ridges. 
The investigations of Zuckerkandl lead to the conclusion that 
the original number of these ridges was comparatively small, and 
that where, among Mammals, we have a large number or a 
more complicated form of turbinal, they have been secondarily 
acquired in the interest of a greater physiological efficiency. 
Most orders of Mammals, e.g. the greater number of Carnivora, 
Rodentia, Insectivora, Lemuroidea, Marsupialia, with Ornitho- 
rhynchus (Echidna ?), have five olfactory ridges; but the Ungulata 
1 [Kiikenthal has recently worked out the development of the olfactory organ in 
the Delphinide, and has proved (i) that the union of the external nasal apertures 
is a secondary process occurring during Ontogeny, and (ii) that in the young embryo 
well-developed olfactory lobes and bulbs are present which disappear in the adult.— 
Denksch. d. medic. -natur-wiss. Geselisch., Jena, Bd. iii. pp. 326 et seq. | 
