958 SEC. 18. BIOLOGY. 



3953. Chronoscopic Tuning Forks. Set of 4 tuning forks, 

 with 10, 25, 50, and 100 vibrations per second, to be used as 

 chronoscopes ; they have a long, very pliable, flat spring, movable 

 in its plane and perpendicularly on it, in order to be easily applied 

 to the cylinder. Prof. Dondcrs, Utrecht. 



3954. Direct registering Levers (large size) attached to 

 lead wires. Prof. Danders, Utrecht. 



Very light registering levers with a pin (aluminium or cork) resting on 

 the moving object (a contracting muscle, fontanelles, &c.). Two levers, one 

 with a doubly bent pin, fixed on the same stand, can register two movements 

 on the same cylinder, one immediately below the other (the contractions of 

 the auricle and ventricle of the heart of a frog). Comp. Nuel. Onderzoe- 

 kingen gedaan in het physiologisch laboratorium te Utrecht, Ser. 3, T. 11. 

 p. 292, and Pfliiger's Archiv. B. ix. S. 86. 



3955. Apparatus for verifying the Transmission of 

 Movements by Air, an india-rubber tube, and a Marey's 

 Cardiograph. Prof. Donders, Utrecht. 



On a horizontal revolving axis is fixed an eccentrically ground brass disc, 

 which moves a metallic spring placed underneath it. This spring registers 

 its movements on a revolving cylinder, and at the same time presses on a 

 tympanum, which communicates through an india-rubber tube with a Marey's 

 cardiograph. If the cardiograph is made to register on the cylinder 

 immediately under the spring, both curves may be compared. When the 

 disc rotates slowly both curves are alike ; with increasing velocity the 

 difference augments. (Compare the curves ; some are an imitation of 

 physiological curves.) 



3956. Brondgeest's Fansphygmograph. To register the 

 movements of respiration, the beating of the heart, and the pulse 

 of different arteries. Dr. Brondgeest, Utrecht. 



The little box contains : 



1. Cylinder, with internal spring, to be wound up by the hand. 



2. Two Marey's sphygmographs to register on the blackened cylinder 



simultaneously respiration and pulse curve. 



3. Little box with pens, to register, if desired, with ink on white paper. 



4. A large tympanum, to register respiration, to be fastened with a tape 



round the chest or stomach. 



5. Tympanum, with wooden plate and pin enclosed in a hoop, to be applied 



on the heart or on an artery. 



6. Glazed papers for the cylinder. 



7. Curves of respiration and pulse obtained simultaneously with the 



instrument. 



c. CIRCULATION AND RESPIRATION. 



3957. Scheme of the Circulation of the Blood (for instruc- 

 tion). Prof. Donders, Utrecht. 



An elastic bag with valves sucks water up from a vessel. By repeatedly 

 pressing on the bag (with a lever) undulations are produced either in a glass 

 or into an elastic tube, producing an interrupted or a continuous flowing out. 

 On a long bent elastic tube the simultaneous existence of streaming and pro- 



