724 OF REPRODUCTION. 



for the determination ; since, during the two latter months of pregnancy, the 

 increasing development of the lower extremities throws it lower down. 



Embryo 3 to 4 weeks. It has the form of a serpent ; its length from three to five lines ; 

 its head indicated by a swelling ; its caudal extremity (in which is seen a white line, indi- 

 cating the continuation of the medulla spinalis), slender, and terminating in the umbilical 

 cord; the mouth indicated by a cleft; the eyes by two black points; the members begin 

 to appear as nipple-like protuberances ; the liver occupies the whole abdomen ; the bladder 

 is very large. The chorion is villous, but its villosities are still diffused over the whole surface. 



Embryo of 6 weeks. Its length from 7 to 10 lines; its weight from 40 to 75 grains; 

 face distinct from cranium ; aperture of nose, mouth, eyes, and ears perceptible : head 

 distinct from thorax ; hands and fore-arms in the middle of the length, fingers distinct; 

 legs and feet situated near the anus ; clavicle and maxillary bone present a point of ossifi- 

 cation ; distinct umbilicus for attachment of cord, which at that time consists of the om- 

 phalo-meseraic vessels, of a portion of the urachus, of a part of the intestinal tube, and of 

 filaments which represent the umbilical vessels. The placenta begins to be formed; the 

 chorion still separated from the amnion; the umbilical vesicle very large. 



Embryo of 2 months. Length from 16 to 19 lines; weight from 150 to 300 grains; the 

 elbows and arms detached from the trunk ; heels and knees also isolated ; rudiments of 

 the nose and of the lips; palpebral circle beginning to showjtself; clitoris or penis ap- 

 parent ; anus marked by a dark spot ; rudiments of lungs, spleen, and supra-renal capsules ; 

 ccecum placed behind the umbilicus; digestive canal withdrawn into the abdomen; 

 urachus visible ; osseous points in the frontal bone and in the ribs. Chorion commencing 

 to touch the amnion at the point opposite the insertion of the placenta; placenta begins to 

 assume its regular form; umbilical vessels commence twisting. 



Embryo of 3 months. Length from 2 to 2^ inches; weight from 1 oz. to 1^ oz. (Troy); 

 head voluminous; eyelids in contact by their free margin: membrana pupillaris visible; 

 mouth closed; fingers completely separated; inferior extremities of greater length than 

 rudimentary tail ; clitoris and penis very long; thymus as well as supra-renal capsules 

 present ; ccecum placed below the umbilicus ; cerebrum 5 lines, cerebellum 4 lines, me- 

 dulla oblongata 1^ line, and medulla spinalis J of a line, in diameter; two ventricles of 

 heart distinct. The decidua reflexa and decidua uterina in contact: funis contains umbili- 

 cal vessels and a little of the gelatine of Warthon ; placenta completely isolated ; umbilical 

 vesicle, allantois, and omphalo-mesenteric vessels have disappeared. 



Fatus of 4 months. Length 5 to 6 inches; weight 2^ to 3 oz. ; skin rosy, tolerably 

 dense; mouth very large and open; membrana pupillaris very evident ; nails begin to 

 appear: genital organ and sex distinct ; ccecum placed near the right kidney; gall-bladder 

 appearing; meconium in duodenum; coecal valve visible; umbilicus placed near pubis ; 

 ossicula auditoria ossified; points of ossification in superior part of sacrum; membrane 

 forming at point of insertion of placenta on uterus; complete contact of chorion with 

 amnion. 



Fcetus of 5 montJis. Length 6 to 7 inches ; weight 5 to 7 oz. ; volume of head still com- 

 paratively great; nails very distinct; hair beginning to appear; 'skin without sebaceous 

 covering; white substance in cerebellum; heart and kidneys very voluminous ; ccecum 

 situated at inferior part of right kidney ; gall-bladder distinct ; germs of permanent teeth 

 appear ; points of ossification in pubis and calcaneum ; meconium has a yellowish-green 

 tint, and occupies commencement of large intestine. 



Foetus of 6 months. Length 9 to 10 inches: weight 1 Ib. ; skin presents some appear- 

 ance of fibrous structure; eyelids still agglutinated, and membrana pupillaris remains; 

 sacculi begin to appear in colon; funis inserted a little above pubis; face of a purplish 

 red; hair white or silvery; sebaceous covering begins to present itself; meconium in 

 large intestines; liver of dark red; gall-bladder contains serous fluid destitute of bitter- 

 ness; testes near kidneys ; points of ossification in four divisions of sternum ; middle 

 point at lower end of sternum. 



F(Etus o/7 months. Length 13 to 15 inches; weight 3 to 4 Ibs. ; skin of rosy hue, thick, 

 and fibrous ; sebaceous covering begins to appear ; nails do not yet reach extremities of 

 fingers; eyelids no longer adherent; membrana pupillaris disappearing; a point of ossi- 

 fication in the astragalus ; meconium occupies nearly the whole of large intestine ; valvular 

 conniventes beginning to appear; ccecum placed in right iliac fossa; left lobe of liver 

 almost as large as right; gall-bladder contains bile; brain possesses more consistency; 

 testicles more distant from kidneys ; middle point at a little below end of sternum. 



Foetus of 8 months. Length 14 to 16 inches; weight 4 or 5 Ibs. ; skin covered with 

 well-marked sebaceous envelope; nails reach extremities of fingers; membrana pupillaris 

 becomes invisible- during this month; a point of ossification in last vertebra of sacrum; 

 cartilage of inferior extremity of femur presents no centre of ossification ; brain has some 



