THE ORGANS OF SENSATION 183 



Goat has 12 circumvallate papillae with 15,400 taste-buds. 

 Sheep 24 9,600 



Calf 24 35,200 



Neither is the transverse diameter of the taste-buds greatest 

 in man, as the following table shows : 



Man 0*0396 mm. maximum transverse diameter. 



Dog 0-0306 



Cat 0-0324 



Roe-deer 0*0468 ,, 



Ox 0-0480 



Pig o*o2OO-o'O52i mm. 



Sheep 0-0360-0*0540 ,, 



A special organ of taste with very variable structure is the 

 so-called marginal organ (Oppel), formerly known as "Mayer's 

 organ," consisting of papillae with taste-buds situated on the 

 edge of the tongue. Csokor l describes these marginal papilla:: 

 in rabbits, horses, pigs, dogs and cats only, not in man, but 

 Mayer himself had found them in man years previously, and 

 has been corroborated by later observers. 



On the other hand, the foramen caecum situated at the 

 angle of the circumvallate papillae is not met with save in man 

 (and then only in about 50 per cent, of individuals) ; this repre- 

 sents the common orifice of several mucous glands (the ductus 

 excretorius of Bochdalek) and a part of the thyroglossal duct. 



At the tip of the tongue occur Nuhn's glands which secrete 

 by five ostia both mucus and saliva. Originally discovered 

 only in man and the oran-utan, 2 they have recently been 

 shown by Von Podwisotzky to be present also in sheep. 3 



5. Sense of Hearing, Like the other higher senses 

 nothing definite is known of the auditory apparatus in the 

 lower animals. 



It has been conjectured that among Coelenterata the mar- 

 ginal vesicles of the medusae which contain crystals are organs 

 of hearing, solely, however, on the analogy of these crystalline 

 bodies with the otoliths of higher orders; similar vesicles 



1 Ellenberger's Histologie, pp. 527-48. 



2 J. Hyrtl, Anatomic des Menschen, 6th ed., 1859, p. 556. 



3 A. Oppel, loc. cit., Part III., p. 218. 



