VOL. XIII.] PHILOSOPHICAL TRANSACTIONS. 6l5 



morbid strabismus, or more violent contortion of those muscles after great con- 

 vulsions of the nerves^ causes always a double vision. 



5. It has been urged that the tension of all the fibres of the optic nerves 

 might be uniform, notwithstanding the greater flexure of the superior; because 

 these latter might be longer, and consequently might not have a greater stress 

 upon the thalami optici then the lateral : as, if the arm of a tree grows bent, the 

 fibres on the protuberant part seem not more stretched than on the concave side, 

 but to take only a longer compass. To which I answer that sense evinces the 

 contrary in our case, and if any one draws out the optic nerve straight forward 

 from the thalamus opticus, he will plainly see that the top fibres press more on 

 the subjacent medullary protuberances than the lateral, or make a deeper im- 

 pression. 



6. It has been urged that the action of vision was uniform, and therefore re- 

 quired an uniform tension of all the fibres. To which I answer, that though in 

 the view of the entire object, or its place by both eyes, it ought to be so, and 

 that therefore it was done by correspondent fibres ; yet in a stricter view of the 

 parts of the same object by one eye, there is a discrimination. 



7. Lastly it has been urged that the fibres of the choroides seem more 

 adapted to vision than those of the retina, because these last did not sistere 

 species, as transmitting the colours of the former; and besides some blood 

 vessels running among them would interrupt the image; and lastly sensation 

 could be better continued to the tense fibres of the pia mater by the one, than 

 to the brain by the softer of the other. 



^n Account of the Dissection of a Bitch, ivhose Cornua Uteri being filled with 

 the Bones and Flesh of a former Conception, had after a id Conception the Ova 

 affixed to several Parts of the Abdomen. By a Physician, F. R. S, N° 147, 

 p. 183. 



It would seem a needless thing to publish an observation, to confirm the 

 opinion of the production of animals from eggs, which is almost universally re- 

 ceived: but that some time since the learned Diemerbroeck, and very lately 

 Mons. Verney have endeavoured to confute and expose it. The most con- 

 siderable argument they use is taken from the narrowness of the Fallopian tubes, 

 where they open into the womb, and at their extremities. But, though these 

 authors lay a great stress on the structure of that passage, it cannot be accounted 

 of any force, when ocular demonstration is brought against it ; and the eggs are 

 discovered in the entrance, and afterward to have made their way through them 

 into the womb. 



