PULSE. 



181 



and the neck constricted. The mouth opens 

 upon the summit of the head, and is guarded 

 in front by two longitudinal prominent lips 

 (d, d], beneath which is a pointed, fleshy ap- 

 pendage (e). 



The fins (//), attached to the sides of 

 the neck, are fleshy and much smaller than in 

 either of the preceding genera. 



The branchiae (g,g) are situated at the op- 

 posite extremity of the animal, and form two 

 prominent lines somewhat in the shape of two 

 capital Cs placed back to back and united 

 by a transverse band. These lines give off 

 from each side small prominent laminae, ar- 

 ranged much in the same way as the leaflets 

 of a pinnate leaf. 



On the right side of the body, and a little 

 above the branchial apparatuses seen a simple 

 prominent line (h), which, on opening the 

 animal, is discovered to be the branchial vein 

 opening into the auricle of the heart (i), 

 which, enclosed in its pericardium, is situated 

 upon this side (&). 



On opening the integument, which is com- 

 paratively soft, the mass of the viscera is 

 found to be enclosed in a muscular envelope, 

 the fibres of which are almost all longitudinal 

 (Jig. 115. 4, /, /). The pericardium is not con- 

 tained within this fleshy envelope, which is 

 only adherent to the skin in the vicinity of 

 the branchiae ; for in this place are situated 

 the arterial trunks, which convey the blood of 

 the body into the pulmonary organ. 



On dividing the muscular layer (fig. 115. 

 5 and 6), it is seen that almost the whole 

 space within is nearly equally shared between 

 the liver (m), the testicle (n), and the ovary (o), 

 the latter being slightly the largest viseus of 

 the three. The ovary occupies the bottom of 

 the visceral sac, the testicle is on the left, and 

 the liver on the right side. 



The stomach is very capacious, and sur- 

 rounded on all sides by the liver, which pours 

 the bile directly into its interior through nu- 

 merous orifices, exactly as in Conchiferous 

 Mollusks. The walls of the stomach are thin 

 and internally present numerous little cavities, 

 into which the biliary pores open (Jig. 115. 7, 

 p). The rectum is short, and opens beneath 

 the right fin (Jig. 115. 7, g). 



The mouth is a fleshy mass of considerable 

 size, from which two fleshy appendages are 

 prolonged backwards (Jig. 1 15. 7, 8, r r). The 

 tongue is covered with short reverted spines, 

 the use of which is evidently to assist in de- 

 glutition (Jig. 115. 8, .v). The posterior part 

 of the mouth, in which the tongue is situated, 

 is separated from the anterior (Jig. 1 15. 7, 8, u), 

 which is membranous, by a fleshy construction 

 (Jig. 115. 8, ttt), upon which are perceived 

 three small tubercles. 



The opening of the mouth is guarded by 

 two bunches of tentacula (Jig. 1 15. 1 to 8, c), 

 which the animal can, at will, either protrude 

 or retract within the oral orifice. Each of 

 these tentacles consists of a delicate filament, 

 terminated by a minute tubercle excavated in 

 the centre. These organs forcibly remind us 

 of the complicated oral apparatus of the Clio 



already described, and most probably are in- 

 struments of prehension analogous to those of 

 the Cephalopoda. 



The salivary glands (Jig. 1 15. 7, 8, v v) are 

 long and ample, and their excretory duct, as 

 it passes above the brain, is obviously dilated 

 (W). 



The brain (fg. 1 15. 9, y) is a narrow trans- 

 verse band, and among the nerves which it 

 furnishes, two may be observed on each side, 

 which are connected beneath the oesophagus 

 with a group of six ganglia, four of which are 

 mesial arid of considerable size, while the other 

 two placed at the sides are of smaller dimen- 

 sions. 



There is nothing peculiar in the structure 

 of the generative apparatus, which nearly 

 resembles that of Hyalea and Clio. The 

 penis is small, and situated beneath the mouth. 

 It is protruded between the two little lips 

 situated upon the anterior surface of the head 

 (j%. 115. 1, 5, d d). The common generative 

 orifice is found immediately in front of the 

 anus, and is prolonged externally into a kind 

 of furrow, which is directed forwards. 



(T. Rymer Jones.) 



THE PULSE (Gr. fffvypos, a-jv^a, Lat. 

 Pulsus, Fr. Pauls, Ger. Puts, Dut. Pols, Ital. 

 Polso, Span. Pulso). The nature and cause 

 of the pulse have already been examined in an 

 earlier part of this work.* It is proposed to 

 consider it, in this place, as a separate and 

 independent subject, and to bring together the 

 leading facts which have been ascertained, in 

 reference especially to that property which is 

 most readily submitted to examination, namely, 

 its frequency. 



Our knowledge of this subject is little more 

 than a century old ; for though Quetelet f at- 

 tributes to Kepler, who was born towards the 

 end of the 16th century, the idea of ascer- 

 taining the number of pulsations in a given 

 time, Floyer, who wrote at the beginning of the 

 18th century, was the first who collected any 

 considerable number of observations. Bryan 

 Robinson J, Falconer , Knox ||, Graves 5F, 

 Nick **, and Quetelet -}-f followed in the same 

 field of inquiry, and still more recently 

 the writer of this article. The facts which 

 these authors placed on record have not yet 

 been brought together in any standard treatise 

 on physiology ; so that a clear and connected 

 exposition of the frequency of the pulse, as it is 

 affected by age, sex, posture, exercise, food, and 

 other natural causes, and of the relation which 

 it bears to the respiration, is still a desideratum. 



* Art. CIRCULATION, Vol. i. p. 638. 



f Sur 1'Homme, vol. ii. p. 80. 



J A treatise on the Animal Economy, by Bryan 

 Robinson, M.D., 1732. 



Observations respecting the Pulse, &c., by "W. 

 Falconer, M.D. F.R.S., Bath, 1796. 



I Ed. Med. and Surg. Journal, vol. xi., 1815, and 

 No. 131, 1837. 



f Dublin Hospital Reports, vol. v. 1830. 



** Beobachtungen iiber die Bedingungen, unter 

 denen die Haiifigkeit des Pulses im Gesunden Zus- 

 tand verandert wird. Von Georg. Heinrich Nick. 



ft Op.cit. 



N 3 



