512 PHILOSOPHICAL TRANSACTIONS. [aNNO 1795. 



ever led me on, but I have been actuated solely by an irresistible impulse to 

 observe ; and because I certainly shall never have reason to be ashamed of the 

 observations I have laid before the world, which have always conducted me to 

 new truths. 



Mr. S. next states further explanations and correspondence of computations 

 of the twilight, together with remarks on the other properties of the atmosphere 

 of Venus. First observing, that as the celebrated author of the paper so often 

 mentioned, " on the planet Venus," though he confirmed my discovery of the 

 twilight of Venus's atmosphere, yet represents the computation of it as not de- 

 monstrated, and positively as very inaccurate, which may, without any foundation, 

 be injurious to the truth, it becomes my duty to give some explanations and re- 

 marks, that persons skilled in those matters may be better able to form a right 

 judgment of my new computation, which agrees excellently with the old one; 

 ' and at the same time may determine, whether there be inaccuracy and error, and 

 on whose side it lies. Some calculations then follow, with a view to justify his 

 former assumptions and calculations, as to the apparent diameter of the sun (44') 

 viewed from Venus, and the twilight of Venus's atmosphere, &c. From which 

 he infers ; Thus, by these new measurements and computations, the general 

 results I have already deduced in my above-mentioned paper " on the atmospheres 

 of Venus and the moon," relative to the atmosphere of Venus, are still more 

 confirmed and justified; and there is no longer any doubt, as my opponent agree- 

 ing with me allows, that the atmosphere of this planet is very dense, like that of 

 the earth, 



VI. Experiments on the Nerves, particularly on their Reproduction; and on tlie 

 Spinal Marrotv of Living Animals. By IFilliam Cruihshanh, Esq. p. 17 7. 

 The nerves on which these experiments were made are, the par vagum, and 

 intercostal. The par vagum arise from the basis of the brain, pass through the 

 basis of the skull, along with the internal jugular veins. They are dis- 

 tributed to the tongue, oesophagus, larynx, heart, and lungs; and, running on 

 each side of the oesophagus, may be said to terminate in the stomach, liver, and 

 semilunar ganglion of the intercostals, below the diaphragm; whence they 

 are again distributed to the viscera of the abdomen. The intercostals also arise 

 from the basis of the brain, pass through the basis of the skull, along with the 

 carotid arteries. They at first run by the fore part of the vertebra; of the neck, 

 still adhering to the coats of these arteries; but having reached the chest, they 

 leave these arteries, and run before the heads of the ribs, where, sending off 

 branches which pass between the ribs, they have thence been named intercostals. 

 Several of these branches uniting, form a trunk on each side, which running 



