without lo-s of blood and expo-e the heart. Determine which vagus 

 contain- the inhibitory liber-. 



_'7<). .Iction of nicotine. Apply nicotine solution i o._" , i to the 

 ventricle. After a few minute-, stimulate the trunk i f the vagus 

 nerve. Xo curve need be written. I- the heart inhibited? Xo\v 

 lift the heart with a i;las- rod, and stimulate the intra-cardiac inhi- 

 bitor) nerve-, i.e.. at simi-auricular junction or white crescent. 

 l\e-ult? Nicotine parali/.e- -onie inhibitory mechanism between 

 the vagus and the intra-cardiac inhibitory nerves. I hit it is known 

 that nicotine docs not paralyze nerve trunks. Hence it is probable 

 that the cardiac inhibitory liber- in the vagus do not pass to the 

 cardiac mu-cle directly but end in o ntact with nerve cells which 

 take up the impulses, and transmit them through their proces-e- to 

 the muscular libers of the heart. 



jSi). Atropine. \\'itli a clean pipette apply a few drops of a 

 solution of atropine (o.$ f < i to the heart. After a few moments lift 

 the ventricle and stimulate the crescent. Is the heart inhibited: 

 Atropine paralyses the intra-cardiac inhibitory nerves. 



281. M nsairinc. With a line pipette put upon the ventricle a 

 tew drops of salt solution containing a trace of muscarine. Kffect ? 



jSj. Antagonistic action of muscarine and atropine. With a 

 fresh pipette apply a little salt solution containing atropine (0.5', ). 

 Result? 



/'. rRl-SSi'kl- AND VELOCITY CONDITIONS IX Till-'. 

 CIRCULATION. 



283. Circulation in the <\v/> of the fi'oi/'s foot. Kthcri/e lightlv 

 a trog and adju-t on the t rog board with the web between the toes 

 Stretched over the hole in the board. Study the circulation under 

 the microscope and draw. ( >b-crvc the following pi tints: 



a. Veins, arteries, capillaries I b>\\- can yon distinguish them? 



b. \\hich pulsate and in which i- the vclocitv fa-test and in 

 which -1' \\c-t ? Why ? 



c. < >b-ervc under the high power movements of individual red 

 and white corpn-clc-. Are tbe-e found in particular regions of 

 the vessel? Why? 



d. Watch for a white corpuscle passing through the wall of 

 the capillarv. 



_'K|. I 'lace a tiny drop of glacial acetic acid (from the point 

 of a pini on the web. Note the effect of the irritant, change- in 

 -i/c of \e--cl-. collection ,,f leucocyte-, etc. l^o not //<'/ acid on the 

 lens of the inicroscope. 



