582 Proceedings of the British Association. 



Mr. Blackwall read a paper on the Palpi of Spiders. It was a 

 report of his researches with reference to this snbject, since he made a 

 communication to the Association at its meeting at Cambridge. The 

 practical result of most consequence appeared to be that the full 

 developement of the palpal organs indicates a state of maturity in male 

 spiders, and this knowledge will be useful in preventing the arach- 

 nologist from falling into the too common error of mistaking young 

 spiders for old ones, and of describing them as distinct species. 



Mr. Patterson expressed a hope that Mr. Blackwall would pursue 

 his researches, and draw up a report on the subject for their next 

 meeting. This was acceded to by Mr. Blackwall. 



Section E.— MEDICAL SCIENCE. 



Dr. Sargent read a communication from Sir David Dickson, contain- 

 ing a report of a case of ascites with enormous distension, the abdomen 

 containing twenty-nine imperial quarts of very viscid straw-coloured 

 serum; and a case of sudden death, from the bursting of a thoracic 

 aneurism. 



Prof. Williams read a paper ' On the Construction and Application of 

 Instruments used in Auscultation.' To express the acoustic law ac- 

 cording to which all improvements in the stethoscope must be at- 

 tempted, he deemed of great importance ; and this law he stated to be, 

 that sounds are best conducted by bodies of an elasticity or tension 

 resembling that of the sonorous body ; on the other hand, bodies 

 differing in elasticity are bad recipients of each other's vibrations. 

 Thus, sounds produced in air (vocal and breath sounds) are best trans- 

 mitted by an enclosed column of air ; those produced by solids (those 

 of the heart, rhonchi, friction) are better communicated by rigid solids 

 of moderate density. He proceeded to shew how these principles were 

 applicable to explain the form and material he has adopted in the 

 stethoscope, and detailed a number of experiments by which he de- 

 monstrates the imperfection of the proposed flexible stethoscope, which 

 only transmitted the sounds explored through the inclosed column 

 of air in its central cavity. On the other hand, the assertion of Dr. 

 Cowan, though supported by Prof. Forbes, that plugging the cavi- 

 ty of the rigid wooden stethoscope does not materially impair its 

 efficiency, Prof. Willliams proved, by experiment, to be erroneous ; 

 but the impairment is least when the aurile end of the instrument 

 is plugged. In making experiments of this kind, he insisted on the ne- 

 cessity of having some faint sound as a test sound (as the opticians 



