ACIDS, ANIMAL. ACRITA. 



47 



ACIDS, ANIMAL. Several acids are 

 found in animal products, some of which are 

 peculiar to organized bodies, and others com- 

 mon to them and to the other kingdoms in 

 nature. The former are characterized by their 

 analogy to other organic compounds, and are 

 ternary or quaternary combinations of carbon, 

 hydrogen, oxygen, and nitrogen. The latter 

 are for the most part binary compounds, such 

 as the phosphoric, carbonic, muriatic, sul- 

 phuric, and fluoric acids. 



With the exception of lactic acid, the exis- 

 tence of which as a distinct definite compound 

 is doubtful, there is only one acid which can 

 strictly be called peculiar to animals, namely, 

 the uric acid. The oxalic, benzoic, and acetic 

 acids are common to animals and vegeta- 

 bles. 



The other animal acids are not found ready 

 formed, but are artificially produced by various 

 chemical processes in which animal matters are 

 concerned. Such are the various acids from 

 fat and oil, the animal pyroacids, the purpuric 

 acid,* and a few others. There are also cer- 

 tain acids almost peculiar to individual animals, 

 such as the formic,f the allantoic or amniotic,j 

 the bombic, &c., and one or two which are the 

 products of disease. 



Under the articles FAT, URINE, MILK, and 

 BONE, will be found the details respecting the 

 principal animal acids. 



( W. T. Brande.) 



AC RITA (a, priv. xgivu, discerno,} a pri- 

 mary division of the animal kingdom founded by 

 Virey, and so called by Macleay,|| composed of 

 the lowest classes of the radiate animals of 

 Cuvier, and characterised by an indistinct, dif- 

 fused, or molecular condition of the nervous 

 system. 



The necessity for a dismemberment of the 

 Radiataof Cuvier, which Rudolphi^F justly calls 

 a chaotic group, has been felt, and directly or 

 indirectly expressed, by most naturalists and 

 comparative anatomists.** It is impossible, in- 

 deed, to predicate a community of structure 

 in either the locomotive, excretive, digestive, 

 sensitive, or generative systems, with respect to 

 this division, as it now stands in the " Regne 

 Animal." 



As in the animal organization the nervous 



1 First obtained by Dr. Prout from the pure 

 lithic acid, of which the excrements of the boa 

 constrictor consist. 



t Procured from the expressed liquor of ants. 



t Supposed by Vauquelin to exist in the liquor 

 amnii oi the cow. 



Extracted by Chaussier from the silk-worm, 

 but its existence is very problematical. 



tHorae Entomologicae, vol. i. pt. ii. p. 202. 

 Synopsis Entozoorum, p. 572. 

 ' Lamarck observes, " Les animaux apathiques 

 (as he terms the Acrita) furent tres-improprement 

 appeles zoophytes: ils ne tiennent rien de la nature 

 vegetale, et tous generalemeut sont completement 

 des animaux. La denomination d'animaux ra- 

 yonnes ne leur convient pas plus que la prece- 

 'lente ; car elle ne peut s'appliquer ; qu'a une partie 

 dVntr'eux ; et il s'en trouve beaucoup parmi eux 

 qui n'ont absolument rien de la forme rayonnante." 

 Aniin. sans Vertebres i. p. 390. 



system is that which is subject to the fewest 

 varieties, and as its relative perfection is the 

 surest indication of the relative perfection of 

 the entire animal, the modifications of this 

 system necessarily indicate the highest or pri- 

 mary divisions of the animal kingdom, and 

 form their distinguishing characters. 



Taking, then, the nervous system as a guide, 

 the radiata of Cuvier will be found to re- 

 solve themselves into two natural groups, of 

 which the first, composed of the Polyastric In- 

 fusoria of Ehrenberg, the Polypi of Cuvier, 

 the Entozoa parenchymatosa, Cuv. or Sterel- 

 mintfia, and the Acalephte, differs in the absence 

 or obscure traces of nervous filaments from 

 the second division, including the Echinoderma, 

 the Entozoa cavitaria or Ccelelmintha, the epi- 

 zoa, and the Rotifera, Ehr., in which nervous 

 filaments are always distinctly traceable, either 

 radiating from an oral ring, or distributed, in a 

 parallel longitudinal direction, according to the 

 form of the body. 



These different conditions of the nervous 

 system are accompanied with corresponding 

 modifications of the muscular, digestive, and 

 vascular systems, and a negative character, ap- 

 plicable to the higher division of Cuvier's 

 Radiata, may be derived from the generative 

 system. 



With respect to the muscular system, we find 

 that although all the Acrita possess the loco- 

 motive faculty at some period of their exist- 

 ence, and many never become fixed, yet that 

 distinct muscular fasciculi are not necessarily 

 developed. In the fresh-water polype, for ex- 

 ample, the whole of the homogeneous paren- 

 chyma of which it consists is equally con- 

 tractile ; and even in the medusa, which ranks 

 among the highest of the Acrita, no distinct 

 muscular organs for effecting the contractions 

 of the gelatinous disc have yet been detected. 

 In the higher division of radiata, on the other 

 hand, which from the filamentous condition of 

 the nervous system may be termed Nemato- 

 neura, the muscular system is always distinctly 

 eliminated. 



The difference in the condition of the diges- 

 tive system between the Acrite and Nemato- 

 neurous classes is still more striking : in the 

 former the alimentary canal is excavated in the 

 parenchyma of the body, and is devoid of dis- 

 tinct parietes : in the Nematoneura it is pro- 

 vided with a proper muscular tunic, and floats 

 in an abdominal cavity. 



A corresponding difference is presented by 

 these two divisions of the invertebrate animals, 

 in the condition of the vascular system. Where 

 traces of sanguiferous organs are met with in 

 the Acrita, they are equally with the digestive 

 organ devoid of proper parietes, but consist 

 of reticulate canals in the substance of the 

 body, generally situated near the surface, and 

 in which a cyclosis of the nutrient fluids is 

 observed analogous to that of plants, but not 

 a true circulation. This structure obtains in 

 the Acrita as low down in the scale as the poly- 

 gastrica, in which class Ehrenberg has deter- 

 mined the existence of a superficial network 

 of vessels containing an opaline fluid. In those 



