Franklin P. Mall 451 
find. this rib much more common in the embryo than we think it is,— 
possibly in 5% of the specimens. 
The arches—The arches of the vertebrae appear on the 57th day as two 
small granules of bone, one for the second vertebra and one for the 
eighth. On the next day these two points of ossification have increased 
on both sides of the embryo. In the cervical region the first and second 
arches are present on the right side and the first three arches are on the 
77 
TABLE V. 
Giving the times of ossification of the bodies of the vertebri. 
| 
INO serie d Jadnaccoces 202/274'263, b, 2/266:263, b, 1272/282/284/288, b|/M|N 300) O} S8|/806,c) Q'806,a306,b) P| R 
Mere thee ceciscicteiciieisiete 30) 31) 32 33) 34 34) 42) 54) 57 (69/70) 73/73/75) 75 (81/109 ie 105/110 
INN SS oobos basbogdondG 56] 56 57) 58 58) 65) 73) 75 |8383) 858587) 87 (901100 105 (105110 
loa. Pen llee 36 al Dolke Wlladiioo “We ae ae | hee phe 
Shr ie lWlske so lode bo WO he os Reyes Ih 8 Gay 
5.. el est era |ieet ileal NOM eye eae Eat 3 
6e es | ee ee * ok | * (IQ * fk * Em IKE aa Nee 
ne omc A ee Sco ee cal ee ap Cele |i cs ¥) |e) |e 
ge co feo [2] © FFL FOR] * fF] * * | * | & 
Gi he leo | eo i) £2 cS ee ey ep ce 4) Me ea ee ullet 
1055 Foie | e3 || es es | ea yy toy ta IE * | & | & 
Tit * |e] xe] oe & fe] # ig fe] # fe] # * |e le 
12.. aes |) te IS ee liye || ee Bale * | * | # 
ise xe] e |e] * & fe) # ig fe] * fe] x * |e] x& 
Bodies of | 14. rae je dal PRE * #& ik | * 0 * | x |* * Eat Se 3 
the aps xi|alae| oe oo |e #19 | * fe] # * | # | # 
Vertebree | 16. | 2 eae 
1%. | ee eee ie ee ee | ee ae le 
18. w]e] ae] ok oe fe fe fe ie] oe fe] oe | ok | & | 
19. #l*x]e| oe «i]t ie] « ie] x | & | & | 
20. el ala)] « «i |x ie ie | x le | x * | * | * 
2]. ele} e| # «fe |e ie le] & fe | x x | «| * 
29 | PS |fes || e3 * ox ik | & le fe ES Esa eS FS eS) eS 
| 93. ES || ead) es |) C3 62 (E> Peay 3 ee S| es * || 
DAs ele] | oe oe fe | & be fe * * * oer |e 
Shae Allee ele le] oe oe tele te oe] oe fe] oe | oe | | & 
6. | * | oe & fe | fe fe] oe fe | x | |2|* 
ee Sea (oe | * Se £ (| & |e be *” lk =] oe te 
aes lea er 2 os rene. | 
heer ee | ‘le | a # : 
| | 
left side. Lower down the 7th to the 10th arches inclusive are on the 
right side and the 8th to the 11th on the left side. In embryo 272 and J, 
all the arches are present to the 19th, 7. e., through the cervical and tho- 
racic region on both sides; on the 64th day they extend to the third lumbar 
vertebra. The next day they extend to the 13th vertebra only, and on the 
72d day they reach to the 27th vertebra. From now on the ossification 
centers are irregular in number, fluctuating around the first sacral 
vertebra. A glance at Table IV shows that the lower vertebre vary in 
their appearance, corresponding somewhat with the condition found in 
the appearance of the ribs. 
Up to the 65th day the second arch is the largest in the cervical region 
