My dear Sir,

I do not know how to thank you enough for the very great trouble which you have taken in writing at such length, & for your kind expressions towards me.² I am particularly obliged for the abstract with respect to Sir C. Bell’s views, as I shall now proceed with some confidence; but I am intensely anxious to read your essay in full when translated & published, as I hope, in the Dublin Journal.³ As you speak of the weak-point in the case, viz; that injuries are not known to follow from the gorging of the eye with blood, I may mention that my son & his friend at a Military Academy, tell me that when they perform certain feats with heads downwards, their faces become purple & veins distended, and that they then feel an uncomfortable sensation in their eyes, but that, as it is necessary for them to see, they cannot protect their eyes by closing the eyelids.⁴ The companions of one young man who naturally has very prominent eyes, used to laugh at him when performing his feats, & declare that some day both eyes w^d start out of his head.

Your essay on the physiological & anatomical relations between the contraction of the orb-muscles & the secretion of tears is wonderfully clear, & has interested me greatly. I had not thought about irritating substances getting into nose while vomiting; but my clear impression is that mere retching causes tears; I will however try to get this point ascertained.⁵ When I reflect that in vomiting, (subject to the above doubt) in violent coughing from choking, in yawning, violent laughter, in the violent downward action of the abdominal muscle as during the evacuation of fæces when constipated, & in your very curious case of the spasms,—that in all theses cases, the orb-muscles are strongly and unconsciously contracted; & that at the same time tears often certainly flow, I must think that there is a connection of some kind between these Phenomena; but you have clearly shewn me that the nature of the relation is at present quite obscure.⁶

With the most cordial thanks for your great kindness | believe me | my dear Sir | yours sincerely obliged | Charles Darwin