172 PHILOSOPHICAL TRANSACTIONS. [aNNO 1667- 



of water when the brain has received a wound or an alteration by some dis- 

 temper. 



3. He has taken a particular care of examining the optic nerve in divers ani- 

 mals, it being one of the most admirable productions in the brain. Having 

 therefore, among other fishes, dissected the head of a xiphias or swordfish, which 

 has a very large eye, he has not observed any considerable cavity in the optic 

 nerve, nor any nervous fibres ; but found that the middle of this nerve is 

 nothing else but a large membrane folded according to its length in many 

 doubles almost like a fan, and invested by the dura mater. Eustachius, a 

 celebrated anatomist, had written something of this before, but obscurely, and 

 without mentioning the animal wherein he had made this observation. 



4. He thought he should have met with the same thing in terrestrial animals, 

 but he found that fishes alone have such a structure of the optic nerve : for that 

 of an ox, pig, and other such animals is nothing but a heap of many small 

 fibres of the same substance with the brain, wrapped about with the dura 

 mater, and accompanied with many little blood-vessels. Hence he decides that 

 great question among anatomists, whether the optic nerve be hollow or not ? 

 For, says he, it cannot be otherwise but there must be many cavities in this 

 nerve, forasmuch as the small filaments of which it is composed cannot be so 

 closely joined that there should not be some void space between them. 



5. Concerning the tongue, the same author has discovered in it many little 

 eminences, which he calls papillary, and believes to be the principal organ of 

 taste. 



[See Number 2,0 of the Transactions, page 135, where a full account is 

 given of this last discovery, from the treatise of Bellini de Organo Gust{is.] 



A71 Experiment of Sig. Fracassati upon Blood grown Cold, 



N' 27, p- 493. 

 When blood is suffered to become cold in a dish, that part which is beneath 

 the superficies appears much blacker than that on the top; and it is vulgarly 

 said, that this black part of the blood is melancholy blood, and men are wont to 

 make use of this example to show, that the melancholy humour, as it is called, 

 enters with the three others into the composition of the blood. But Signior 

 Fracassati maintains that this blackish colour comes from hence, that the blood 

 which is underneath is not exposed to the air, and not from a mixture of 

 melancholy : to prove which he assures, that upon its being exposed to the air 

 it changes colour and becomes of a florid red.* 



* This observation, made so many years ago by Fracassati, contains the germ of the modern 

 theory of the oxygenation of the blood in the lungs. 



