Houses (Places)
Have you ever wondered why there are 12 houses and not 8 or 6? You can find those in the history of Astrology especially some attempts in the Hellenistic period but the Hellenistic Astrologers fixed the number of houses at 12 because they used Whole Sign Houses to examine the topics in a person's life (or issues related to an event).
I have my Ascendant in Leo. The Hellenistic Astrologers called the Ascendant the Horoskopos, whic best translates as hour marker. In the whole sign system my Leo Ascendant has significance in the main because it determines that Leo is the rising domicile or sign and thus Leo becomes my first place (or house in modern terminology). That is not just the portion of Leo that has greater degrees than my Ascendant but the whole of the sign of Leo.
Virgo becomes my second place, Libra my third, Scorpio my fourth and so on, ending with Cancer as my twelfth place. This system does not allow intercepted houses, it does not break down in high latitudes (North or South) and there's no room for debate about where the house divisions are. My second house starts at 0 Virgo and that's it.
As I once posted elsewhere a very crude version of this is used by Sun Sign columns, which assume that the sign that your Sun is in, is the rising sign and hence your first house (or place). Sun sign columns use the other signs as place markers for the house - so if Venus is in Aries, for me with a Libra Sun, that would be treated as a transit of the Seventh.
This actually points to one use that can be made of Whole Sign Houses, when you know your Ascendant. In the example above, Venus is actually transiting my ninth house and that's where the influence will be felt, not in my seventh. Venus will affect my ninth from the moment it enters Aries till the moment it leaves - planetary ingresses therefore become important.
One consequence of the move to Whole Sign Houses is that while your Ascendant and Descendant remain in the first and seventh houses/places resepectively, your MC and IC can 'float' around at the top and bottom of your chart. Commonly you can find the MC in the eleventh, tenth or ninth houses by Whole Sign, and occasionally in the eighth or twefth for extreme latitude births..
The MC and IC were not ignored, they were treated as sensitive points and if they fell outside the tenth, the signification of that house was blended in to the interpretation of the tenth. Thus Robert Hand, the Astrologer, actually has his MC in the ninth place and the ninth amongst other things signifies divinatory techniques in general and Astrology in particular - the significations of the ninth are relevant to career matters.
Quadurant houses - those using the Ascendant, Descendant, MC and IC as house cusps were actually developed in the very early Hellenistic Period but for most of it they were used specifically to assess planetary strength in the length of life technique.
Whole sign houses were used well into the Ninth Century by Astrologers such as Masha'allah and Sahl ibn Bishr but sometime afterwards they fell out of use. Why that happened we don't know for certain. Hand has speculated that it was through a mis-translation at some point. Brennan has speculated that it might come from confusion about Ptolemy. Ptolemy uses the Whole Sign House system, though he never explicitly says so (it is clearly implicit though) but in Book 3 of the Terrabiblios, (the third of four books) he goes into the length of life calculation and like all Hellenistic authors he uses a quadrant house system. In this case he explains how to calculate the houses. This seems to have led to a belief that this was his preferred system, when it wasn't. To make things even worse, Ptolemy's explanation was not clear and there are several medieval texts suggesting alternative systems as the one that Ptolemy meant. Thus Ptolemy may inadvertently have caused the multiplicity of house systems used today Ptolemy's text is the one Astrological text that remained continuously available between the second century and the 21st century and therefore was for long periods the only available Hellenistic text. Thus attempts to get back to a 'pure original' form of Astrology tended to be associated with a 'Back to Ptolemy' approach.
Does all of this invalidate quadrant house systems? No it doesn't but it does suggest that using Whole Sign Houses can be a useful addition to the astrologer's repertoire. There does seem to be an increasing interest in the system not just from Traditional Astrologers, but from all branches of Astrology. There was a recent poll on the Facebook Professional Astrologers group on house systems used and Whole Sign Houses featured strongly as a system used or intended to be used.
Some useful links are:
http://www.hellenisticastrology.com/2011/12/08/did-ptolemy-use-whole-sign-houses/
http://theastrologypodcast.com/2013/07/18/house-division-in-astrology/