HYDATIDS. 



II VUH ACIDS. 



which fills the proper cyt of a bydatM u almost always colourless 

 and liinpiii. Thr liquid uf the common cyt in which they float 

 nay prKMit vwiuui appearance* : sometimes it U quit/- limpid ; at 

 aHiin it may be coloured. When formed in the liver it in often 

 yellow. 



The principal furnu of cystic entosoa, or true hydatids, recognised by 

 Ku<llpui and other* are called Cyatioereus, (Vniiriin, and Ki-hiim- 

 ooociu; to which may be added Aeephalocysti*. Several specie* 

 of Cystieercus are enumerated, but the most common are C. tenuic.illin, 

 and C. cellulomw. The former (Ta-nia hydatigena, I'ullat ; Hyilitw 

 globosa, Lamar*-t\ if met with frequently in the |>eritoneum and pleura 

 of ruminating animals and |>igs. it i often generated in the disease of 

 beep called the rot, where another entoaxxm, the " diatom*," or fluke- 

 worm, is met with in the ducts of the liver. The C. oellulosus (Tienia 

 eellulosa et T. finna. Urn. ; Hydatis linna, Biun.) is found generally 

 lodged in the tissue of the muscles between the fibres ; it occurs some- 

 times in man, but more frequently in animals, particularly in the hog, 

 where it causes the disease called measles or leprosy. Of the genus 

 Cenurus (Hydatis |x>lycephalus, Ztder), the species C. cerebralis 

 (Tsrnia veniculnris, 6W ; T. cerebralis, Horn.; Polycephalua <>viim.. 

 Zedir) is found in the brain of sheep, oxen, and other ruminating 

 animals. These hydatids occur in various parts of the brain of sheep, 

 but most frequently in one of the lateral ventricles, where they occasion 

 a kind of giddiness, in which the animal turns round and round in one 

 direction ; this affection is denominated by the German fanners " das 

 Drehen," by the French " le Tournis," and in England the sheep are 

 said to be " giddy," or to have the " staggers." 



Sometimes the hydatid is situated in the fourth ventricle, when it is 

 said to cause a variation in the affection, called in German l i.- 

 Springen," from the animal springing up. Kmlolpht says that he has 

 seen the latter variety occur when one large hydatid has occupied the 

 middle part of the brain. In the first case one-half of the body is 

 rendered partially paralytic from the pressure of the hydatid on the 

 side of the brain, and the opposite muscles by their action turn the 

 body round towards the unaffected side. In the latter form of the 

 disease, Kudolphi says that the equilibrium between the anterior and 

 posterior muscles of the body is destroyed, which causes the animal to 

 spring up. Sometimes two hydatids are found in the name ventricle, 

 and occasionally as many as five or six have been met with. The 

 internal surface of the ventricle* is always smooth, and never contracts 

 any adhesion to the cysts. This hydatid is sometimes found as large 

 M a hen's egg ; the walls of the bladder are very thin and fibrous ; and 

 may be seen clearly to contract. The little worm-like bodies attached 

 to it are scarcely half a line in length, and have the power of retracting 

 themselves within the cyst. These hydatids are most generally met 

 with ill yearling cattle and sheep, and their production, or that of the 

 state of health which gives rise to them, seems owing principally to 

 the effects of cold and damp, and watery paaturage, which also 

 occasions the rot in sheep. The best treatment is removal to a dry 

 and sheltered pasturage, in some cases sheep have been cured l>y the 

 extraction of the hydatids by the operation of trepanning. Whenever 

 any of these forms of hydatids are swallowed by man or the lower 

 animals they proceed to develope themselves into tape-worms. 



The hydatids belonging to the genus Echinococcus are commonly 

 called granular hydatids, from the presence of numerous granules or 

 minute particles, which are young hydatids which float in the fluid of 

 -t or adhere to its walla. Two species of Echinococcus have been 

 particularly described : one called E. hominis, has been met with in 

 the brain and abdomen of man in a few instances ; the other, !'.. 

 vetcrinonini, occurs more frequently in the hog and other animals. 



The Accphalocyst, or common globular hydatid, to which it i 

 thought by some that the name of hydatid should be restricted, is a 

 simple unattached vesicle, van-ing in size from a millet-seed to a child's 

 head, filled with iwllucid fluid, furnished with no kind of appendix or 

 head, generally associated with numerous others, and contained in a 

 common cyst, which is also filled with fluid. These bodies seem to 

 poBScsi a proper vitality, though dc|*nileiit for existence on the body 

 of tin- .inim.il in which they live. They are probably undeveloped or 

 alui'Tinal forma of the more definite xpecies. 



till- nny be developed slowly, and occasion BO little incon- 

 n-e, that persons in whom they have been discovered after death 

 may not have suspected disease of the organ in which they existed 

 during life. Occasionally they cause so much irritation that Hiippura- 

 tion may take place either around or within the common nac, which 

 may burst externally or into a serous mucous cavity. In either the 

 first or last case the hydatids will be discharged, and the patient may 

 recover ; but if the cyst should communicate with a serous cavity, as 

 the peritoneum or pleura, fatal inflammation will occur. 



With respect to the treatment for the prevention or removal of 

 hydatids, it is very imperfect. A* they generally occur in a cachectic 

 or disordered state of health, those remedies may be given which are 

 molt likely to remove that state and improve the general i 

 When a hjditid cyst U situated so near the surface of the body that 

 it may be easily evacuated, without risk of effusion into the internal 

 serous cavities, it may sometimes be punctured with propriety, which 

 operation will cause obliteration of the sac. ( WORMS.) 



Pseudo or false hydatids are simple serous cysts or vesicles, either 

 occurring singly or aggregated in clusters, but in both cues having a 



uiore or less dote connection with the subjacent tissues, from which 

 in fact they grow. The vesicles often found in the rliri<l plexuses 

 belong to this dais ; also the cysta which contain the fluid in ovarian 

 dropsy, which may grow to an enormous size. Lastly, me of the moat 

 common situations for these false bydatids is in the uterus, where 

 they are described as " vesicles of a round or oval shape, with a 

 narrow stalk to each, by which they adhere on the outside to one 

 another." They may here increase in such numbers M to distend 

 the uterus till it is too large to be contained in the pelvis, and rises 

 into the abdomen. These cyst* may be developed in many other 

 xituations, and contain fluids of various characters. For further 

 information respecting them we must refer to a |perbyl>r limit-kin. 

 in ' Med. Chirur. Trans.,' vol. xv., p. 266. 



II VI HI A (constellation, BSpoi in Ptolemy), the Water-snake, o 

 the old constellations. From the time of Aratus downward* it has 

 always been a triple figure : a long snake, represented a* trailing upim 

 the ground, bears upon his back a cup (Crater), and nearer to his tail 

 is seated a crow (Corvus). The mythological meaning is altogether 

 unknown. 



The great length of this constellation has caused it to be divided 

 into four parts, which are designated as Hydra, Hydra et ' 

 Hydra et Corvus, and Hydro continuatio. The first contains the head 

 and body up to about 104 hours of right ascension, all near to and 

 south of the bright star Uegulua ; the second contains the cup aud the 

 |kirt* of the body adjacent ; the third the crow, with the part* of the 

 body adjacent; and the fourth (beginning at about IS hours of right 

 ascension) contains the tail. For the third part see i 

 Flamsteed's catalogue Hydra and Hydra: continuatio are treated in all 

 respects as two distinct constellation*, with Corvus and Hydra ot Crater 

 intervening. Hr. Baily, in his new edition of the catalogue, ha* 

 treated the two as .one constellation, and numbered the stars accord- 

 ingly, making 1, 2, Ac., Hydnc continuation!* to be 45, 46, 4c., 

 Hydnc. 



HYDRA. 



No. in Catalogue 

 No. in Catalogue of British 



Character. 



Character. 



y 



HYDROS CUNTINUATIO. 



No. in Catalogue 

 No. in Catalogue of British 

 of Flamsteed. Association. 



4450 

 4685 



Magnitude. 

 4 

 4 

 4 

 4 

 4 

 J 

 4 

 4 

 4 

 4 



Magnitude. 

 4 



4 

 4 



4 

 4 

 I 



Magnitude. 

 8-5 

 4 



HYDRACIDS. Acid* have been divided into oxa, ids and 



In the former, an elementary lx>dy is combined with m 



supposed acidifying principle ; and in the latter, a substance, usually 



an elementary one, in united with hydrogen as the imaginni 



[>ower. 

 The class of hydracids contains some which have l.o-ii ah,.,.lv 



treated of, a* hydrohromic and hydrochloric aciil ; otlicr.< i 

 described. With respect to the general properti.-, of hvdi 



be remarked that their acidity is in general 



that they contain only one equivalent, of hydrogen, aud that 



acted ujion by metallic oxides they lose their hydrogen 



lining with the oxygen of the oxide, and the results are water 



laloid salt : thus, to put one of the most familiar cases, when hydro- 

 chloric acid is added to soda, or the oxide of sodium, the result 

 a hydrochlorate of soda, but chloride of sodium and water. \\l"n. 



lowever, hydrochloric acid is united to bates which cont.iin no oxy- 

 gen, then real hydrochlorates are the result : thus, ammonia, which i 



i powerful alkaline base, combines with hydrochloric acid to form 



lydrochlorate of ammonia, or sal ammoniac. So, also, when the same 

 acid unites with morphine, or any other oxygenous vegetable alkaloid, 



t is admitted that the resulting compound is a hydrochlorate of mor- 



