. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. ARACHNIDA. 209 dilatation which the scorpions carry at the end of the tail ; it is terminated by a little sharp hook generally curved backwards. Near its termination there may be observed, as in the mandibnlous hook of spiders, a very minute orifice, or, according to some authors, two dis- tinct fissures. It is from this part that a lim- pid fluid, having strongly-marked poisonous qualities, exudes; and, corresponding to the fo- ramen within, there is the neck of a little blad- der which is the true secretory organ. Litt
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. ARACHNIDA. 209 dilatation which the scorpions carry at the end of the tail ; it is terminated by a little sharp hook generally curved backwards. Near its termination there may be observed, as in the mandibnlous hook of spiders, a very minute orifice, or, according to some authors, two dis- tinct fissures. It is from this part that a lim- pid fluid, having strongly-marked poisonous qualities, exudes; and, corresponding to the fo- ramen within, there is the neck of a little blad- der which is the true secretory organ. Little is known respecting its structure: according to the observations of Treviranus it is surrounded by a horny substance and provided with a muscle, which most probably has for its func- tion the compression of the vesicle and the consequent expulsion of the poison. Apparatus for secreting the fluid which con- cretes in the air.—This apparatus is peculiar to certain arachnidans : it does not exist in the scorpions nor in many other genera ; but when present it is always situated at the posterior part of the body. The threads by which the spiders suspend themselves, and of which they spin their webs, are emitted from the extre- mity of the abdomen. There we find, in the vicinity of the anal aperture, several small appendages, which it is important not to con- found with one another, (Jig. 96.) Of these there are two which are small articulated hairy Fig. 96. and filiform processes (b b ; )* the others are spinnarets, or the or- gans by which the silky threads are emit- ted. Of the latter, four may generally be counted, (c d.) Their structure is very re- markable; it has been described by many anatomists, and among others by Lyonnet in his posthumous Memoirs. This patient anato- mist has discovered that the surface of each of the spinnarets is pierced by an infinite number of minute holes, from each of which there escapes as many little drops of a liquid, which, becoming dry th
Size: 1497px × 1668px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, booksubjectanatomy, booksubjectphysiology, booksubjectzoology
