SALIVA. 



415 



apparatus, suppose that the spermatic fluid is 

 secreted in the tubes, and passed on to the 

 vesicle, where it is projected into the cloaca, 

 and fecundates the ovum. The constant con- 

 traction of the vesicle seems opposed to the 

 view that its function is that of merely fecun- 

 dating the ovum, and Dujardin thinks it is 

 connected with the function of respiration. 

 Hitherto no spermatozoa have been found in 

 these organs, although Doyere states that he 

 has found zoospores in the tardigrade In- 

 fusoria. The spermatic tubes are seen in 

 Rotifer vulgaris (fig. 299. , i), in Hydatina 

 senta (fig. 293. h), and Notommata myrmeleo 

 (J!g.3Q3.f,g). 



After the extrusion of the ova from the 

 cloaca in many species, they are attached to 

 the lorica, as in Brachionus pala (fig. 296, /!), 

 in the same way as in some Crustacea. The 

 rapidity with which the ova are produced is 

 very great ; and one individual, in the course 

 of a few days, will be the parent of many mil- 

 lions. Their reproductive powers, however, 

 are small compared with those of Polygastria. 



In this brief sketch we have occasionally 

 alluded to the affinities of the Rotifera, and 

 we think that there can be little doubt, that 

 these are decidedly with the Articulata, stand- 

 ing perhaps between the cilio-branchiate Polyps 

 on the one side, and the Cirrhopoda on the 

 other. Ehrenberg has summed up the general 

 relations of these creatures in the following 

 manner. They are 



Polygastria, with a single intestinal canal, 

 without the power of spontaneous fission. 



Acalepka, with a simple intestinal canal, and 

 rotatory organs. 



Nematoid worms, with rotatory organs and 

 united sexes. 



Bryozoa, without gemmiparous reproduc- 

 tion. 



Mollusca, without vascular pulsations. 



Entomostraca, without pulsation or arti- 

 culated feet, and hermaphrodite reproduction. 



Fishes without a backbone or a heart, and 

 with rotatory organs and united sexes. 



BIBLIOGRAPHY. Leeuwenhoek, Philosophical 

 Transactions, 17011704. Baker, Employment of 

 the Microscope. London, 1753. Bory St. Vincent, 

 Dictionnaire Classique d'Histoire Naturelle, art. 

 ROTIFERES. Ehrenberg, Infusions-thierchen. Berlin, 

 1838. Pritchard, Infusoria, living and fossil. London, 

 1845. Doytre, Memoire sur les Tardigrades ; Ann. 

 des Sc. Nat. 1842. Owen, Lectures on Comparative 

 Anatomy, vol. i. London, 1843. Grant, Outlines 

 of Comparative Anatomy. London, 1843. T. Rymer 

 Jones, A general Outline of the Animal Kingdom. 

 London, 1841. Dujardin, Histoire Naturelle des 

 Zoophytes, Infusories. Paris, 1843 ; Report on the 

 Progress of Zoology, 1842, published by the Ray So- 

 ciety. Oken, Phisio-Philosophy, Ray Society, 1847. 

 Mantell, Thoughts on Animalcules. London, 1846. 

 Carpenter, Cyclopaedia of Natural Science. London, 

 1847. (Edwin Lankester.) 



RUMINANTIA. (See SUPPLEMENT.) 



SALIVA (la Salive, Fr. ; der Speichef, 

 Germ.; la Sciliva, Ital.). The saliva is a 

 fluid secreted by a series of glands placed 

 about the maxllary region. These glands, 



viz. the parotids, submaxillaries, and sub- 

 linguals, pour their secretions into the cavity 

 of the mouth on either side. In consequence 

 of this arrangement, it has always been a 

 matter of difficulty to obtain saliva in a per- 

 fectly pure state, the secretion of the mouth 

 interfering, by admixture, with the exhibition 

 of the natural qualities of the saliva, and more 

 especially with its microscopic characters. It 

 occasionally happens that the fluid can be ob- 

 tained more directly from the gland in cases 

 of salivary fistula affecting the parotid duct, 

 but it is to be doubted whether we ought to 

 look for the secretion in its normal state in 

 such instances. No attempts have, as yet, 

 been made to determine whether or not saliva, 

 as obtained from the different glands, is iden 

 tical in character ; but so far as general ob- 

 servation guides us, there appears no variation 

 in its constitution as secreted from these dif- 

 ferent sources. 



Quantity. The quantity of saliva secreted 

 during the day has never been very accurately 

 ascertained. It has been said that about twelve 

 ounces are produced during the twenty-four 

 hours, but it is highly probable that much more 

 than this is excreted by the adult in health. 

 The data for the statement above mentioned 

 are most imperfect. Mitscherlich made expe- 

 riments on a patient suffering from fistula of 

 the stenonian duct, and succeeded in obtaining 

 about 2 ounces troy of saliva from the one 

 parotid in twenty-four hours. The saliva col- 

 lected during the same time from the mouth 

 amounted in this experiment to six times 

 more than that collected from the one gland : 

 we may, therefore, conclude that the subject 

 of this experiment was secreting from 16 

 to 20 ounces troy of saliva during the twenty- 

 four hours. Mitscherlich observed that when 

 the nerves were not excited by the motion of 

 the muscles of mastication, or of those of the 

 tongue, no saliva flowed, but that motion of 

 these parts induced secretion. 



The presence of food in the mouth caused 

 a rapid flow of saliva, which was more espe- 

 cially noticed when the first portions were in- 

 troduced. Long mastication appeared to 

 cause excessive secretion, and the more sti- 

 mulating the nature of the food, the larger 

 was the quantity of saliva produced. 



The uses of the saliva will be best con- 

 sidered when we have described its general 

 qualities. 



Physical qualities. The constitution of 

 saliva has been investigated by several che- 

 mists. It possesses the following general 

 physical characters : When freshly ob- 

 tained from the mouth it is opalescent, vis- 

 cid, and colourless. It separates by rest 

 into an upper stratum of clear fluid, and a 

 lower portion made up of the same fluid in 

 admixture with epithelium scales and mucus. 

 Under the microscope, saiiva shows the pre- 

 sence of epithelium scales swollen mucus 

 globules, and substances of various forms, ap- 

 parently shreds of scales and ruptured cells. 

 There are also fatty particles, varying in size, 

 and bright granules. Some of the mucous 



