ASSAMAR 



261 



limb dip s under the surface of tho mercury, n, in the tube B. B is a small test-tube, 

 widened at the bottom in three directions, and containing a few millimetres in depth 

 of mercury, n. It is fastened with sealing-wax to A, and is provided with a cork, 

 tho, one orifice of which admits the tube c ; through tho other passes tho bent 

 tube d. 



The lower extremity of the tube / being placed far down a sink, and a gradual 

 stream of water being allowed to enter by c, as indicated by (1), the water in A rises 

 (2), tho air is driven out of A (3), bubbles through tho mercury, n, and passes by d 

 (4), through the apparatus employed. During this filling of A with water, tho mer- 

 cury, m, prevents tho retrograde flux of water through h. After A is filled, tho water 



rises in the tubes /and e until it reaches the top of/, when this tube acts as a syphon 

 (ft'), and being wider than the ingress tube c, gradually empties tho bottle A (6). To 

 supply tho place of this water, the air must enter by h (7'), and may thus be drawn 

 through the apparatus in use, while the mercury n, in B, prevents the regression of 

 the air through e. 



Tho instrument has of course a simpler form when required to act only as an 

 aspirator, for then the tube B and its appendages may bo dispensed with. 



When an increased resistance has to be overcome (the instrument being used either 

 as aspirator or as expirator), tho tube/ is drawn further out of the tube g. 



This form of spirator has been found to be certain in its action ; for with a con- 

 tinuous stream of water, the volume of air which passes through is in definite pro- 

 portion to the volume of water employed ; and, indeed, the slower stream of water 

 tho more nearly equal are these volumes, for in this case tho amount of water passing 

 through c during the action of tho syphon/, is inconsiderable. 



-assATCETlDA. (Assus, dried ; fa'tidus, fetid.) A fetid gum-rosin obtained 

 from the root of tho Narthex Assafaetida, and probably from some other species belong- 

 ing to tho UmbeUiferce. 



ASSAMAR. (Assure, to roust ; Amarus, bitter.) A name given to the bitter 



