The Bursa pharyngeal was at one time looked upon as the place

whence the pituitary body had been derived from the roof o the phars nx, but this is now disproved and its meaning is unknown The tonsil is formed in the second bronchial cleft or rather pouch, lor the clefts are largely incomplete in man, about the fourth month; its lymphoid tissue, as well as that elsewhere in the pharynx, is formed from lymphocytes in the subjacent mesenchyme (see EMnnvotocv), though whether these wander in from the blood or are derived from original mesenchyme cells is still doubtful. The Middle turbinated bone Superior meatus of nose

these form the simplest type of true internal gills. In the larval lamprey (Ammocoetes) there are eight gill slits opening from the pharynx, but in the adult (Petromyzon) they are reduced to seven, and a septum grows forward separating the ventral or bronchial part of the pharynx from the dorsal or digestive part. Both these tubes, however, communicate near the mouth. In fishes there are usually five pairs of gill slits, though a rudimentary one in front of these is often present and is called the spiracle. Occasionally, as in Hexanchus and He tanchus, there may be six or seven slits, andp the evidence of comparative anatomy is that fishes formerly had a larger number of gill slits than at present.

Sph°“°'d“1 smug In the Teleostomi, which include the Middle meatus of nose bony fishes, there is an external gill cover or Inferior turbinated bo e opercu um-I°f°“° § °§ f, ';§ n in the Dipnoi or mud fish the work of the gills is shared by that of the lungs, and in the African form, Protopterus, external gills, posmior edge of msalseptum developed from the ectodermal parts of the Gemoglossus

Gemohyoid / /

Lymph and follicle

Hyoid bone

(From Ambrose Binnmgham, Cunninghanfs Text Book of Anatomy) Sagittal Section through Mouth, Tongue, Larynx, Pharynx and Nasal Cavity. The section is slightly oblique, and the posterior edge of the nasal septum has been preserved The specimen is viewed slightly from below, hence in part the low position of the inferior turbmated bone.

development of the ventral part of the pharynx is dealt with in the articles TONGUE and RESPIRATORY SYSTEM. For literature see Quain's Elements of Anatomy, vol i. (London, 1908), and I P. McMurrich, Development of the Human Body (London, 1906).

Comparatwe Anatomy.-In the lower, water-breathing, vertebrates the pharynx is the part in which respiration occurs. The water passes in through the mouth and out through the gill slits where it comes in contact with the gills or branchiae. The lowest sub phylum of the phylum Chordata, to which the term Adelochorda is sometimes applied, contains a worm-like creature Balanoglossus, in which numerous rows of gill slits open from the pharynx, though Cephalodiscus, another member of the same sub phylum, has only one air of these. In the sub phylum Urochorda, to which the Ascidians or sea squirts belong, there are many rows of gill slits, as there are also in the Acrania, of which Amphioxus, the lancelet, is the type. In all these lower forms there are no true gills, as the blood-vessels lining the large number of slits provide a sufficient area for the exchange o ases.

ii the Cyclostomata a reduction of the number of gill slits takes place, and an increased area for respiration is provided by the gill pouches lined by pleated folds of entodermal mucous membrane; Orifice o

gill slits, first appear. In the tailed Amphibians (Urodela) the first and fifth gill clefts are never perforated and are therefore in the same condition as all the gill clefts of the human embryo, while in the gilled salamanders (Necturus and Proteus) only two gill clefts remain patent. The gills in all the Amphibia are external and of ectodermal origin, but in the Anura (frogs and toads) these are succeeded before the metamorphosis from the tadpole stage by internal gills, which, unlike those of fish, are said to be derived from the ectoderm.

In the embryos of the Sauropsida (reptiles and birds) five gill clefts are evident, though the posterior two are seldom at any time perforated, while in the Mammalia the rudiments of the fifth cleft are no longer found in the embryo, and in man, at al events, none of them are normally perforated except that part of the first which forms t e Eustachian tube. It will thus be seen that in the process of phylogeny there is a gradual suppression of the gill cle ts beginning at the more posterior ones.

The soft palate is first found in crocodiles as a membranous structure, and it becomes f Eustachian tube

pharyngeal

Part of the

pharyngeal tonsil

Lateral recess of

harynx

P

Levator cushion

aryngea o d

Glands in soft

late

Anterior palatine

arch

f

P

Salpingo-

ph l f

P3-

Supratonsillar

ossa

lica triangular is

Tonsil

s Posterior palatine

eplglottic fold

Cricoid cartilage

arch

Epiglottis muscular in mammals. The bursa pharyngeal and pharyngeal tonsil are found in several of A, , y, eno the lower mammals. In the sheep the latter is particularly large.

For literature and further details, see R. Wiedersheim's Comparatwe Anatomy of Vertebrates, translated by W. N. Parker (London, 1907); also Parker and Haswell's Zoology (London, 1897). (F. G. P.)

PHEASANT (Mid. Eng. fesaunt and fesaun; Ger. fasan and anciently fasant; Fr. faisan-all from the Lat. phasianus or phasiana, sc. avis), the bird brought from the banks of the river Phasis, now the Rioni, in Colchis, where it is still abundant, and introduced, according to legend, by the Argonauts into Europe. Judging from the recognition of the remains of several species referred to the genus

Phosianus both in Greece and in France,^[1] it seems not impossible that the ordinary pheasant, the P. colchicus of ornithologists, it may have been indigenous to this quarter of the globe. If it was introduced into England, it must almost certainly have been brought by the Romans;^[2] for, setting aside several earlier records of doubtful authority,^[3] Stubbs has shown that by the regulations of King Harold in 1059 onus phasianus is prescribed as the

1. ↑ These are P. archiaci from Pikermi, P. altus and P. medius from the lacustrine beds of Sansan, and P. desnoyersi from Touraine, see A. Milne Edwards, Ois. foss. de la France (ii. 229, 239–243).
2. ↑ Undoubted remains have been found in excavations at Silchester.
3. ↑ Among these perhaps that worthy of most attention is in Probert's translation of The Ancient Laws of Cambria (ed. 1823, pp. 367, 368), wherein extracts are given from Welsh triads, presumably of the age of Howel the Good, who died in 948. One of them is, “ There are three barking hunts: a bear, a squirrel and a pheasant.” The explanation is, “ A pheasant is called a barking hunt, because when the pointers come upon it and chase it, it takes to a tree, where it is hunted by baiting." The present writer has not been able to trace the manuscript containing these remarkable statements so as to find out the original word rendered “ pheasant " by the translator, but a reference to what is probably the same passage with the same meaning is given by Ray (Synops. meth. animalium, pp. 213, 214) on the authority of Llwyd or Lloyd, though there IS no mention of it in Wotton and Clarke's Leges Wallicae (1730). A charter (Kemble, Cod. diplom. iv. 236), professedly of Edward the Confessor, granting the wardenship of certain forests in Essex to Ralph Peperking, speaks of “ fesant hen " and “ fesant cocke," but is now known to be spurious.