32 



illustrating the subject by coloured diagrams, and by prepared specimens shown 

 under the microscope. 



The President, in proposing a vote of thanks to Mr. White for his paper, said 

 he thought the subject was just now a most delicate one to express opinions 

 upon. No doubt it was well-known that quite recently in " Nature" great 

 doubt had been cast upon this organ being a gland at all. 



A vote of thanks to Mr. White was carried unanimously. 



Mr. Curties said he had brought with him to the meeting, and exhibited under 

 his microscope a slide of the same object, prepared by Mr. Tatem, of Reading, and 

 presented by him to the Cabinet of the Club. It was accompanied by the 

 following letter: "I send you three preparations of the Salivary Glands of 

 the Cockroach. They show satisfactorily enough the lobules, sacs and ducts, 

 the latter held open, as in all other insect salivary glands, by spiral filaments, 

 those of the lobes coated with the yellowish epitheleae, glandular structure of 

 Pfliiger. Apropos of these slides is a letter in last week's number of ' Nature,' 

 in which the writer (Mr. Hollis) questions the salivary character of these 

 organs. Certainly as regards the secreting nature of their lobular portions I 

 think there can be no doubt, but I quite concur in his opinion that the sacs are 

 not reservoirs for saliva, as is commonly believed, but for the same reasons ad- 

 vanced by him, I have ever considered them as air sacs only, which, when the 

 adult condition is attained, and the wings fully developed, the insect may 

 possibly inflate, and so effect its migrations by such aids to flight. It is an 

 assured fact that during life, or rather immediately after death, when the dis- 

 section is made, they are always found empty, flattened, and folded on them- 

 selves on either side of the aesophagus, having to be drawn out and spread as in 

 the preparations. Seeing, however, that the common duct opens by a longitu- 

 dinal slit a little in advance of the base of the tongue, I do not see in what way 

 they can be filled with air from without. Can they possibly be inflated from time 

 to time according to the exigencies of the insect, with secreted air, as is the case 

 in the bladders, having no ducts, of some fishes ? But this is mere specula- 

 tion."* 



Mr. B. T. Lowne said that some years ago Dr. Pfliiger made some very in- 

 teresting observations on the salivary glands, and he was, if not the first, cer- 

 tainly one of the first who discovered the ultimate nerve fibres, and who showed 

 that the epithelial cells contained the termination of the nerves. The subject 

 was one which required extreme delicacy in working out, but to his own mind 

 it appeared that the evidence in favour of what Pfliiger said is extremely 

 strong. He had been for a long time engaged upon other matters, and had 

 been unable to give to this subject the attention which he desired. Pfliiger had 

 not demonstrated his points sufficiently to others, but he had long thought that 

 they might be demonstrated, and that this might be done as Pfliiger had done 

 it, by means of chloride of gold, and he trusted that if Mr. White would just 

 try this process he might be able to demonstrate it. The process is an extremely 

 troublesome one, because it was always so very uncertain whether or not the 

 preparations would bo successful. It is as follows : — A very weak solution of 

 Ter-chloride of gold— about a ^ per cent, solution — should be used to soak the 

 perfectly fresh glands in for a longer or shorter period. How long they should 



* Siuce the discussion upon this subject Mr. Tatem has communicated the following': — 

 " I can neither abandon or modify my opinions, based as they are on my own observa- 

 tions and dissections. I have ever found these sacs empty and flaccid, and most commonly 

 folded on themselves— so that they have to be drawn out and spread. If proved to be 

 salivary sacs. I shall conclude that the condition in which I always found them was 

 brought about by the mode of killing the insect by drowning — the sacs becoming emptied 

 and intussusoepted." 



