Reciprocal cross-protective antigens have been demonstrated between types 3 and 31 cocci, and one-way cross-protective antigens have been demonstrated between types 46 and 51 cocci. The reciprocal cross-protective antigen of types 3 and 31 is distinct from the specific M protein of either type. In the one-way cross relationship, type 46 cocci contain both type 46 and type 51 M proteins and therefore stimulate protective antibodies against both types. Type 51 cultures contain only the homologous M antigen. These relationships were demonstrated by capillary precipitin tests, indirect bactericidal tests, and in agar-gel diffusion patterns. The practical significance of these relationships in the serological typing of group A streptococci is discussed along with their possible role in immunity to streptococcal infections in man.

HARRELL. New method of preparing immunizing antigens for the production of anti-M sera against certain serotypes of group A streptococci. J. Bacteriol. 89:141-145. 1965.-Antisera against types 4, 29, 41, and 46 streptococci have been prepared by use of a vaccine killed by adjusting the pH to 11.7 and heating for 1 hr at 56 C. Heating at the high pH destroyed the antigenic material responsible for the major reciprocal crosses present in cells of types 4, 29, and 46 without affecting the M protein. Antisera prepared with the "alkaline-treated" vaccine did not contain the major reciprocal crosses. Antibodies against the M protein were shown to be present by the bactericidal test, failure to react in the precipitin test with acid extracts of homologous trypsinized cells, and retention of the precipitin reaction after absorption with homologous trypsinized cells. The antisera did not react with the "B" antigen of the provisional type B 3264. Type 11 antisera prepared with alkaline-treated vaccine did not contain antibodies against the M protein. The usefulness of this type vaccine, particularly for the preparation of type 4 antiserum, is discussed, as well as its limitations.

This paper follows undergraduate students' engagement with the concept of childhood presented to them during a year-long childhood and youth studies module. Through the application of 'threshold concepts' as concepts which transform students' understandings of a subject, the challenges of learning new ideas or concepts of childhood are described. Findings from the qualitative research presented show students' prior understandings are deeply embedded. The conclusion discusses the pedagogical implications of students 'unlearning' prior knowledge and suggests effective practice in encouraging a more reflective approach. Although discipline specific, the findings will be useful to the teaching and learning of concepts that challenge or undermine students' personal understandings of them.

In November  metal detectorists located a decorated copper-alloy mirror, a single silver Knotenfibel brooch and some pottery sherds at Pegsdon, Shillington, Bedfordshire. Subsequent excavation of the findspot uncovered a Late Iron Age cremation burial pit associated with further pot sherds and a single fragment of calcined bone. The opportunity is taken in this preliminary account to revisit both the occurrence in southern England of the brooch type and to discuss the mirror's decoration in relation to the variation of views as to the British mirror series as a whole, and in particular with regard to other recent mirror discoveries. The burial is discussed in its local context and the possible significance of the topography in relation to the site is highlighted.At Pegsdon, in the parish of Shillington, Bedfordshire, spectacular finds have been made in recent years on the site of an apparently otherwise ordinary Romano-British rural settlement. The settlement lies on the Icknield Way, at the foot of the chalk scarp of the Chiltern Hills, on chalky clay colluvium over a solid geology of Lower Chalk. It extends between Kettledean Farm in the north and Pegsdon Common Farm to the south, centred at TL  . It is on the spring-line and a stream, now ditched, formerly rose on the uphill side of the settlement, just below the m contour line, flowing north west, then west, through the settlement that grew up on its banks from at least the Late Iron Age. The spring source issues from the mouth of a short deep dry valley, about m in length, running north west down the scarp rising to the south east. The scarp rises to about m OD while the settlement is situated on relatively flat ground between the m and m contours. A second small stream, also now ditched, emerges from the ground some m to the north of the settlement ( fig ) and again bisects the settlement, running north to south.Knocking Knoll, a Neolithic short-long burial mound, is sited on top of the scarp, approximately m north of the dry valley and m east of the settlement. Tingley Tumulus, a Bronze Age round barrow, lies on the scarp, close to the head of the dry valley, km south east of the settlement. Knocking Hoe, a very prominent, rounded spur of natural hard chalk, is located at the mouth of the dry valley, on its northern side. Looking from the settlement up and along the scarp, the view of the chalk landscape is indeed impressive.Knocking Knoll still stands proud on the skyline at the m contour after nearly , years; it must have been a focus of attention when it was first constructed in the early third millennium BC, showing as a large mound of white chalk gleaming in the sunshine. By the Late Iron Age/Romano-British periods, after enduring the best part of , years of weathering and erosion, and having become grassed over, it would have still been an impressive feature in the landscape. Even more visually dramatic is the Knocking Hoe spur, which rises to m, and the dry valley winding beneath it downhill towards t...

Group A streptococcus anti-M typing sera that cannot be made specific by absorption with whole streptococcus cells have been absorbed with the soluble and insoluble fractions of ruptured heterologous cells. The technique has been used successfully for preparing specific anti-M sera against eight serotypes of group A streptococcus. The method involves breakage of the absorbing cells in the presence of the antiserum, and incubation of the mixture at 37 C for 1 hr, followed by 3 to 5 days of incubation at 4 C. The procedure is useful for preparing specific antiserum from certain lots of unabsorbed antiserum that otherwise would have to be discarded because of undesirable cross-reactivity.