954 SEC. 18. BIOLOGY. 



exactly one revolution in its new position, and then returns of itself to its 

 original position in order to keep on rotating. Whilst this one revolution is 

 taking place the excitation and contraction curves are marked by a very 

 simple mechanism. The time of duration can he exactly determined by a 

 simultaneous tracing of a tuning fork curve. For investigations on reflex 

 action, especially for measuring the time of the (so called by the exhibitor) 

 " querlietung " (cross conduction), a contrivance is made by means of which 

 two muscle curves can be simultaneously traced. 



In order to determine very exactly the point at which the contraction curve 

 commences, the movement of the muscle is very considerably magnified. As 

 the form of the muscle curve given by this apparatus cannot be depended on, 

 it will not serve for studying its actual details. 



The time of revolution of the glass plate may vary from tAvo to half a 

 second. It was impossible to measure with any apparatus hitherto constructed 

 a space of time of such length with sufficient rapidity. 



The linear velocity of the instrument revolving at its quickest rate amounts 

 to about 2,500 mm. in a second ; values of 0' 001 second can thus be easity 

 measured. 



3799. Methods of Physiological Experiments and 

 Vivisections. Methodik cler pliysiologischen Experiments und 

 Vivisectionen, von E. Cyon ; with Atlas, published by Ricker, of 

 Giessen and Petersburg, 1876. 



Physiological Institute, Leipzig (Prof. Kronecker). 



3800. Apparatus for demonstrating the Pulsations of 

 the Prog's Heart, constructed by E. S. Stohrer. 



Physiological Institute, Leipzig. 



3801. Canula for the frog's heart apparatus, constructed by 

 Osw. Hornn. Physiological Institute, Leipzig. 



3802. Pendulum Commutator, constructed by Baltzer and 

 Schmitz. Physiological Institute, Leipzig. 



3803. Double Myoscope for the examination and demon- 

 stration of the laws of muscular contraction. 



Physiological Institute, Prague. 



The apparatus allows two nerves to be placed in a damp chamber, at the 

 same time in opposite directions, and to be traversed by the same electrical 

 current. The contractions of the muscles connected with them may be read 

 on two dials. 



38O3a. Dr. Sibson's Improved Gastric Canulse. 



3804. Professor Poster's Levers for recording -the Move- 

 ments of the Muscles, Nerves, &c. T. HawJtsley. 



3805. Different Modifications of the Spring Myograph 



of Du Bois-Reymond. Prof* Theodore Schwann, Liege. 



A diapason or tuning fork is added, with a hammer to make it vibrate. 

 By turning the handle placed on the left-hand side the hammer is freed in the 

 first instance, and in the following moment the blackened glass plate. Ex- 



